Another thing I think is fine is “because you watched ____” and suggestions based on that. Like we see a video that the user watched the whole video or liked it, and then we find similar videos to that I don’t think its that invasive and may be helpful.

As long as its transparent and the user has control to use it or not I think thats the key. The fediverse however is enormously privacy and corporate sensitive, so I can see that it is a tight line to walk here.