diff --git a/extensions/likes/js/src/forum/index.js b/extensions/likes/js/src/forum/index.js
index c3309b73e2..5064bc853b 100644
--- a/extensions/likes/js/src/forum/index.js
+++ b/extensions/likes/js/src/forum/index.js
@@ -32,7 +32,7 @@ app.initializers.add('flarum-likes', () => {
   });
   extend('flarum/forum/components/SearchModal', 'defaultFilters', function (filters) {
     if (app.current.data.routeName && app.current.data.routeName.includes('user.likes') && app.current.data.user) {
-      filters.posts.likedBy = app.current.data.user.id();
+      filters.posts.likedBy = app.current.data.user.username();
     }
   });
 });
diff --git a/extensions/likes/locale/en.yml b/extensions/likes/locale/en.yml
index 2efad1149c..42d3024c63 100644
--- a/extensions/likes/locale/en.yml
+++ b/extensions/likes/locale/en.yml
@@ -53,4 +53,4 @@ flarum-likes:
       posts:
         likedBy:
           key: likedBy
-          hint: The ID of the user
+          hint: The ID or username of the user
diff --git a/extensions/likes/src/Query/LikedByFilter.php b/extensions/likes/src/Query/LikedByFilter.php
index 6fdb89c9a2..5398f522a7 100644
--- a/extensions/likes/src/Query/LikedByFilter.php
+++ b/extensions/likes/src/Query/LikedByFilter.php
@@ -13,6 +13,7 @@
 use Flarum\Search\Filter\FilterInterface;
 use Flarum\Search\SearchState;
 use Flarum\Search\ValidateFilterTrait;
+use Flarum\User\UserRepository;
 
 /**
  * @implements FilterInterface<DatabaseSearchState>
@@ -21,6 +22,11 @@ class LikedByFilter implements FilterInterface
 {
     use ValidateFilterTrait;
 
+    public function __construct(
+        protected UserRepository $users
+    ) {
+    }
+
     public function getFilterKey(): string
     {
         return 'likedBy';
@@ -28,7 +34,13 @@ public function getFilterKey(): string
 
     public function filter(SearchState $state, string|array $value, bool $negate): void
     {
-        $likedId = $this->asInt($value);
+        $likedUsername = $this->asString($value);
+
+        $likedId = $this->users->getIdForUsername($likedUsername);
+
+        if (! $likedId) {
+            $likedId = intval($likedUsername);
+        }
 
         $state
             ->getQuery()
diff --git a/extensions/likes/src/Query/LikedFilter.php b/extensions/likes/src/Query/LikedFilter.php
index b291d97eaf..e22cd674be 100644
--- a/extensions/likes/src/Query/LikedFilter.php
+++ b/extensions/likes/src/Query/LikedFilter.php
@@ -13,6 +13,7 @@
 use Flarum\Search\Filter\FilterInterface;
 use Flarum\Search\SearchState;
 use Flarum\Search\ValidateFilterTrait;
+use Flarum\User\UserRepository;
 
 /**
  * @implements FilterInterface<DatabaseSearchState>
@@ -21,6 +22,11 @@ class LikedFilter implements FilterInterface
 {
     use ValidateFilterTrait;
 
+    public function __construct(
+        protected UserRepository $users
+    ) {
+    }
+
     public function getFilterKey(): string
     {
         return 'liked';
diff --git a/extensions/mentions/js/src/forum/index.js b/extensions/mentions/js/src/forum/index.js
index 8091701173..fb5f5fcb17 100644
--- a/extensions/mentions/js/src/forum/index.js
+++ b/extensions/mentions/js/src/forum/index.js
@@ -92,7 +92,7 @@ app.initializers.add('flarum-mentions', () => {
   });
   extend('flarum/forum/components/SearchModal', 'defaultFilters', function (filters) {
     if (app.current.data.routeName && app.current.data.routeName.includes('user.mentions') && app.current.data.user) {
-      filters.posts.mentioned = app.current.data.user.id();
+      filters.posts.mentioned = app.current.data.user.username();
     }
   });
 });
diff --git a/extensions/mentions/locale/en.yml b/extensions/mentions/locale/en.yml
index 661be1b243..7457c54ee6 100644
--- a/extensions/mentions/locale/en.yml
+++ b/extensions/mentions/locale/en.yml
@@ -119,4 +119,4 @@ flarum-mentions:
       posts:
         mentioned:
           key: mentioned
-          hint: The ID of the mentioned user
+          hint: The ID or username of the mentioned user
diff --git a/extensions/mentions/src/Filter/MentionedFilter.php b/extensions/mentions/src/Filter/MentionedFilter.php
index 2c555de981..4c5e11a9ec 100644
--- a/extensions/mentions/src/Filter/MentionedFilter.php
+++ b/extensions/mentions/src/Filter/MentionedFilter.php
@@ -13,6 +13,7 @@
 use Flarum\Search\Filter\FilterInterface;
 use Flarum\Search\SearchState;
 use Flarum\Search\ValidateFilterTrait;
+use Flarum\User\UserRepository;
 
 /**
  * @implements FilterInterface<DatabaseSearchState>
@@ -21,6 +22,11 @@ class MentionedFilter implements FilterInterface
 {
     use ValidateFilterTrait;
 
+    public function __construct(
+        protected UserRepository $users
+    ) {
+    }
+
     public function getFilterKey(): string
     {
         return 'mentioned';
@@ -28,7 +34,13 @@ public function getFilterKey(): string
 
     public function filter(SearchState $state, string|array $value, bool $negate): void
     {
-        $mentionedId = $this->asInt($value);
+        $mentionedUsername = $this->asString($value);
+
+        $mentionedId = $this->users->getIdForUsername($mentionedUsername);
+
+        if (! $mentionedId) {
+            $mentionedId = intval($mentionedUsername);
+        }
 
         $state
             ->getQuery()
diff --git a/framework/core/js/src/forum/components/DiscussionListItem.tsx b/framework/core/js/src/forum/components/DiscussionListItem.tsx
index f8d5df09b9..e71d5597d8 100644
--- a/framework/core/js/src/forum/components/DiscussionListItem.tsx
+++ b/framework/core/js/src/forum/components/DiscussionListItem.tsx
@@ -21,11 +21,14 @@ import type { DiscussionListParams } from '../states/DiscussionListState';
 import Icon from '../../common/components/Icon';
 import Avatar from '../../common/components/Avatar';
 import Post from '../../common/models/Post';
+import type User from '../../common/models/User';
 
 export interface IDiscussionListItemAttrs extends ComponentAttrs {
   discussion: Discussion;
   post?: Post;
   params: DiscussionListParams;
+  jumpTo?: number;
+  author?: User;
 }
 
 /**
@@ -142,7 +145,7 @@ export default class DiscussionListItem<CustomAttrs extends IDiscussionListItemA
     const items = new ItemList<Mithril.Children>();
 
     const discussion = this.attrs.discussion;
-    const user = discussion.user();
+    const user = this.attrs.author || discussion.user();
 
     items.add(
       'avatar',
@@ -181,6 +184,10 @@ export default class DiscussionListItem<CustomAttrs extends IDiscussionListItemA
   }
 
   getJumpTo() {
+    if (this.attrs.jumpTo) {
+      return this.attrs.jumpTo;
+    }
+
     const discussion = this.attrs.discussion;
     let jumpTo = 0;
 
diff --git a/framework/core/js/src/forum/components/PostsSearchSource.tsx b/framework/core/js/src/forum/components/PostsSearchSource.tsx
index acc4cda3cc..f6c44b4f63 100644
--- a/framework/core/js/src/forum/components/PostsSearchSource.tsx
+++ b/framework/core/js/src/forum/components/PostsSearchSource.tsx
@@ -46,7 +46,7 @@ export default class PostsSearchSource implements SearchSource {
     return (this.results.get(query) || []).map((post) => {
       return (
         <li className="PostSearchResult" data-index={'posts' + post.id()} data-id={post.id()}>
-          <MinimalDiscussionListItem discussion={post.discussion()} post={post} params={{ q: query }} />
+          <MinimalDiscussionListItem discussion={post.discussion()} post={post} params={{ q: query }} jumpTo={post.number()} author={post.user()} />
         </li>
       );
     }) as Array<Mithril.Vnode>;
diff --git a/framework/core/locale/core.yml b/framework/core/locale/core.yml
index 9c8c3dc082..db81e0a6dd 100644
--- a/framework/core/locale/core.yml
+++ b/framework/core/locale/core.yml
@@ -915,7 +915,7 @@ core:
 
   # Translations in this namespace are used in messages output by the API.
   api:
-    invalid_username_message: "The username may only contain letters, numbers, and dashes."
+    invalid_username_message: "The username may only contain letters, numbers, and dashes. With at least one letter."
     invalid_filter_type:
       must_be_numeric_message: "The {filter} filter must be numeric."
       must_not_be_array_message: "The {filter} filter must not be an array."
diff --git a/framework/core/src/Api/Resource/UserResource.php b/framework/core/src/Api/Resource/UserResource.php
index 8a5be23013..5160dc3eba 100644
--- a/framework/core/src/Api/Resource/UserResource.php
+++ b/framework/core/src/Api/Resource/UserResource.php
@@ -146,7 +146,7 @@ public function fields(): array
             Schema\Str::make('username')
                 ->requiredOnCreateWithout(['token'])
                 ->unique('users', 'username', true)
-                ->regex('/^[a-z0-9_-]+$/i')
+                ->regex('/^(?![0-9]*$)[a-z0-9_-]+$/i')
                 ->validationMessages([
                     'username.regex' => $translator->trans('core.api.invalid_username_message'),
                     'username.required_without' => $translator->trans('validation.required', ['attribute' => $translator->trans('validation.attributes.username')])
diff --git a/framework/core/src/Discussion/Search/Filter/AuthorFilter.php b/framework/core/src/Discussion/Search/Filter/AuthorFilter.php
index 138cbc975f..8e27bc4f5a 100644
--- a/framework/core/src/Discussion/Search/Filter/AuthorFilter.php
+++ b/framework/core/src/Discussion/Search/Filter/AuthorFilter.php
@@ -44,6 +44,13 @@ protected function constrain(Builder $query, string|array $rawUsernames, bool $n
 
         $ids = $this->users->getIdsForUsernames($usernames);
 
+        // To be able to also use IDs.
+        $actualIds = array_diff($usernames, array_keys($ids));
+
+        if (! empty($actualIds)) {
+            $ids = array_merge($ids, $actualIds);
+        }
+
         $query->whereIn('discussions.user_id', $ids, 'and', $negate);
     }
 }
diff --git a/framework/core/src/Post/Filter/AuthorFilter.php b/framework/core/src/Post/Filter/AuthorFilter.php
index a692481e32..eedf9a650c 100644
--- a/framework/core/src/Post/Filter/AuthorFilter.php
+++ b/framework/core/src/Post/Filter/AuthorFilter.php
@@ -38,6 +38,13 @@ public function filter(SearchState $state, string|array $value, bool $negate): v
 
         $ids = $this->users->getIdsForUsernames($usernames);
 
+        // To be able to also use IDs.
+        $actualIds = array_diff($usernames, array_keys($ids));
+
+        if (! empty($actualIds)) {
+            $ids = array_merge($ids, $actualIds);
+        }
+
         $state->getQuery()->whereIn('posts.user_id', $ids, 'and', $negate);
     }
 }
diff --git a/framework/core/src/User/UserRepository.php b/framework/core/src/User/UserRepository.php
index ca45483ae4..c5a43032ad 100644
--- a/framework/core/src/User/UserRepository.php
+++ b/framework/core/src/User/UserRepository.php
@@ -86,7 +86,7 @@ public function getIdsForUsernames(array $usernames, User $actor = null): array
     {
         $query = $this->query()->whereIn('username', $usernames);
 
-        return $this->scopeVisibleTo($query, $actor)->pluck('id')->all();
+        return $this->scopeVisibleTo($query, $actor)->pluck('id', 'username')->all();
     }
 
     /**