To hide recognition posts pulled in from the Employee Recognition applet, you'll need the Homepage Manager security role to make changes to the homepage.
Edit the homepage where the Area Timeline applet is located. Hover over the applet and click the three dots to open the configuration settings. In the settings, you’ll find an option labelled Include Recognition posts, which is turned on by default. Toggle this option off to prevent recognition posts from appearing in the timeline.
Once saved, the timeline will no longer display recognition posts.