If we had an open source algorithm for Mastodon/Pixelfed that learned based on the words in the post and image/video we could have a Following + For You feed that showed you all the posts from people you follow and you could choose to see, say, 1 recommended For You post after every 3 posts from your Following feed. With the option to disable For You posts completely or tweak how often you see these.
Discovering new people to follow on mastodon/pixelfed isn’t great (hashtags are rarely used and make posts look ugly) so I still occasionally use twitter because I often discover new indie animators/gamedevs showing off their project making it really nice to browse the For You feed.
This seems like it could have negative side effects. For example if you like posts about negative stories and the algorithm interpreted you being supportive of the post as you appreciating negativity it could work to foster a falsely over negative world view in you sending you into a worse mental state. Or if you dislike a post you might not agree with it could lead to you only seeing posts that reinforce your beliefs to the point of radicalization.
That’s not really how most recommendation algorithms work. A good basic algorithm would be showing you content that the people you follow are following or showing popular posts from a certain category that you tend to like