diff --git a/wcfsetup/install/files/lib/data/article/FeedArticle.class.php b/wcfsetup/install/files/lib/data/article/FeedArticle.class.php
deleted file mode 100644
index 8c5b22880b..0000000000
--- a/wcfsetup/install/files/lib/data/article/FeedArticle.class.php
+++ /dev/null
@@ -1,105 +0,0 @@
-<?php
-
-namespace wcf\data\article;
-
-use wcf\data\IFeedEntryWithEnclosure;
-use wcf\data\TUserContent;
-use wcf\system\feed\enclosure\FeedEnclosure;
-use wcf\util\StringUtil;
-
-/**
- * Represents a viewable article for RSS feeds.
- *
- * @author  Marcel Werk
- * @copyright   2001-2019 WoltLab GmbH
- * @license GNU Lesser General Public License <http://opensource.org/licenses/lgpl-license.php>
- * @deprecated 6.1
- */
-class FeedArticle extends ViewableArticle implements IFeedEntryWithEnclosure
-{
-    use TUserContent;
-
-    /**
-     * @var FeedEnclosure
-     */
-    protected $enclosure;
-
-    #[\Override]
-    public function getLink(): string
-    {
-        return $this->getDecoratedObject()->getLink();
-    }
-
-    #[\Override]
-    public function getTitle(): string
-    {
-        return $this->getDecoratedObject()->getTitle();
-    }
-
-    #[\Override]
-    public function getFormattedMessage()
-    {
-        return $this->getDecoratedObject()->getFormattedContent();
-    }
-
-    #[\Override]
-    public function getMessage()
-    {
-        return $this->getDecoratedObject()->getTeaser();
-    }
-
-    #[\Override]
-    public function getExcerpt(int $maxLength = 255)
-    {
-        return StringUtil::truncateHTML($this->getDecoratedObject()->getFormattedTeaser(), $maxLength);
-    }
-
-    #[\Override]
-    public function __toString(): string
-    {
-        return $this->getMessage();
-    }
-
-    #[\Override]
-    public function getComments()
-    {
-        return $this->getArticleContent()->comments;
-    }
-
-    #[\Override]
-    public function getCategories()
-    {
-        $categories = [];
-        $category = $this->getDecoratedObject()->getCategory();
-        if ($category !== null) {
-            $categories[] = $category->getTitle();
-            foreach ($category->getParentCategories() as $category) {
-                $categories[] = $category->getTitle();
-            }
-        }
-
-        return $categories;
-    }
-
-    #[\Override]
-    public function isVisible()
-    {
-        return $this->canRead();
-    }
-
-    #[\Override]
-    public function getEnclosure()
-    {
-        if ($this->enclosure === null) {
-            if ($this->getImage() !== null) {
-                $this->enclosure = new FeedEnclosure(
-                    $this->getImage()->getThumbnailLink('small'),
-                    $this->getImage()->smallThumbnailType,
-                    $this->getImage()->smallThumbnailSize
-                );
-            }
-        }
-
-        return $this->enclosure;
-    }
-}
diff --git a/wcfsetup/install/files/lib/data/article/FeedArticleList.class.php b/wcfsetup/install/files/lib/data/article/FeedArticleList.class.php
deleted file mode 100644
index f76f441264..0000000000
--- a/wcfsetup/install/files/lib/data/article/FeedArticleList.class.php
+++ /dev/null
@@ -1,38 +0,0 @@
-<?php
-
-namespace wcf\data\article;
-
-/**
- * Represents a list of articles for RSS feeds.
- *
- * @author  Marcel Werk
- * @copyright   2001-2019 WoltLab GmbH
- * @license GNU Lesser General Public License <http://opensource.org/licenses/lgpl-license.php>
- * @deprecated 6.1
- *
- * @method  FeedArticle current()
- * @method  FeedArticle[]   getObjects()
- * @method  FeedArticle|null    getSingleObject()
- * @method  FeedArticle|null    search($objectID)
- */
-class FeedArticleList extends CategoryArticleList
-{
-    /**
-     * @inheritDoc
-     */
-    public $decoratorClassName = FeedArticle::class;
-
-    /**
-     * Creates a new FeedArticleList object.
-     *
-     * @param int $categoryID
-     */
-    public function __construct($categoryID = 0)
-    {
-        if ($categoryID) {
-            parent::__construct($categoryID, true);
-        } else {
-            AccessibleArticleList::__construct();
-        }
-    }
-}
diff --git a/wcfsetup/install/files/lib/page/ArticleFeedPage.class.php b/wcfsetup/install/files/lib/page/ArticleFeedPage.class.php
deleted file mode 100644
index b68bfbbc57..0000000000
--- a/wcfsetup/install/files/lib/page/ArticleFeedPage.class.php
+++ /dev/null
@@ -1,82 +0,0 @@
-<?php
-
-namespace wcf\page;
-
-use wcf\data\article\category\ArticleCategory;
-use wcf\data\article\FeedArticleList;
-use wcf\system\exception\IllegalLinkException;
-use wcf\system\exception\PermissionDeniedException;
-use wcf\system\WCF;
-
-/**
- * Shows a list of cms articles in a certain category in feed.
- *
- * @author  Marcel Werk
- * @copyright   2001-2019 WoltLab GmbH
- * @license GNU Lesser General Public License <http://opensource.org/licenses/lgpl-license.php>
- *
- * @extends AbstractFeedPage<FeedArticleList>
- * @deprecated 6.1 use `ArticleRssFeedPage` instead
- */
-class ArticleFeedPage extends AbstractFeedPage
-{
-    /**
-     * category the listed articles belong to
-     * @var ArticleCategory
-     */
-    public $category;
-
-    /**
-     * id of the category the listed articles belong to
-     * @var int
-     */
-    public $categoryID = 0;
-
-    #[\Override]
-    public function readParameters()
-    {
-        parent::readParameters();
-
-        if (isset($_REQUEST['id'])) {
-            $this->categoryID = \intval($_REQUEST['id']);
-            $this->category = ArticleCategory::getCategory($this->categoryID);
-            if ($this->category === null) {
-                throw new IllegalLinkException();
-            }
-            if (!$this->category->isAccessible()) {
-                throw new PermissionDeniedException();
-            }
-        }
-
-        $this->redirectToNewPage(ArticleRssFeedPage::class);
-    }
-
-    #[\Override]
-    public function readData()
-    {
-        parent::readData();
-
-        // read the articles
-        $this->items = new FeedArticleList($this->categoryID);
-        $this->items->sqlOrderBy = 'article.time ' . ARTICLE_SORT_ORDER;
-        $this->items->sqlLimit = 20;
-        $this->items->readObjects();
-
-        // set title
-        if ($this->category !== null) {
-            $this->title = $this->category->getTitle();
-        } else {
-            $this->title = WCF::getLanguage()->get('wcf.article.articles');
-        }
-    }
-
-    #[\Override]
-    public function assignVariables()
-    {
-        parent::assignVariables();
-
-        WCF::getTPL()->assign([
-            'supportsEnclosure' => true,
-        ]);
-    }
-}
diff --git a/wcfsetup/install/files/lib/page/NotificationFeedPage.class.php b/wcfsetup/install/files/lib/page/NotificationFeedPage.class.php
deleted file mode 100644
index 6c1e684495..0000000000
--- a/wcfsetup/install/files/lib/page/NotificationFeedPage.class.php
+++ /dev/null
@@ -1,48 +0,0 @@
-<?php
-
-namespace wcf\page;
-
-use wcf\system\exception\IllegalLinkException;
-use wcf\system\user\notification\UserNotificationHandler;
-use wcf\system\WCF;
-
-/**
- * Shows a list of own user notifications in feed.
- *
- * @author  Joshua Ruesweg
- * @copyright   2001-2019 WoltLab GmbH
- * @license GNU Lesser General Public License <http://opensource.org/licenses/lgpl-license.php>
- *
- * @extends AbstractFeedPage<\ArrayIterator>
- * @deprecated 6.1 use `NotificationRssFeedPage` instead
- */
-class NotificationFeedPage extends AbstractFeedPage
-{
-    #[\Override]
-    public function readParameters()
-    {
-        parent::readParameters();
-
-        if (!WCF::getUser()->userID) {
-            throw new IllegalLinkException();
-        }
-
-        $this->title = WCF::getLanguage()->get('wcf.user.menu.community.notification');
-
-        $this->redirectToNewPage(NotificationRssFeedPage::class);
-    }
-
-    #[\Override]
-    public function readData()
-    {
-        parent::readData();
-
-        $this->items = new \ArrayIterator();
-
-        $notifications = UserNotificationHandler::getInstance()->getNotifications(20);
-
-        foreach ($notifications['notifications'] as $notification) {
-            $this->items->append($notification['event']);
-        }
-    }
-}
diff --git a/wcfsetup/install/files/lib/system/user/notification/event/AbstractUserNotificationEvent.class.php b/wcfsetup/install/files/lib/system/user/notification/event/AbstractUserNotificationEvent.class.php
index 207195d965..bde9b9e01b 100644
--- a/wcfsetup/install/files/lib/system/user/notification/event/AbstractUserNotificationEvent.class.php
+++ b/wcfsetup/install/files/lib/system/user/notification/event/AbstractUserNotificationEvent.class.php
@@ -3,7 +3,7 @@
 namespace wcf\system\user\notification\event;
 
 use wcf\data\DatabaseObjectDecorator;
-use wcf\data\IFeedEntry;
+use wcf\data\IMessage;
 use wcf\data\language\Language;
 use wcf\data\user\notification\event\UserNotificationEvent;
 use wcf\data\user\notification\UserNotification;
@@ -25,7 +25,7 @@
  */
 abstract class AbstractUserNotificationEvent extends DatabaseObjectDecorator implements
     IUserNotificationEvent,
-    IFeedEntry
+    IMessage
 {
     /**
      * @inheritDoc
@@ -257,13 +257,19 @@ public function getUserNotificationObject()
         return $this->userNotificationObject;
     }
 
-    #[\Override]
+    /**
+     * @return int
+     * @deprecated 6.3 No longer in use.
+     */
     public function getComments()
     {
         return 0;
     }
 
-    #[\Override]
+    /**
+     * @return string[]
+     * @deprecated 6.3 No longer in use.
+     */
     public function getCategories()
     {
         return [