Everything in your main "Home" timeline on Mastodon is there for one of these reasons:
-An account you follow posted it
-An account you follow boosted it
-The post contains a hashtag you follow
-An account you follow replied to an account you also follow
-An account you follow replied to itself
Nothing else gets in your main feed, it's just these things.
If hashtags are at the end of a post they are displayed in a smaller font below the post, which some people miss.
@FediTips I believe that there is another case, which is somewhat a special case of the third point: the post *contained* a hashtag you follow, but was later edited so it no longer does.
The initial hashtag pushed the post into your home feed, but the later edit does not *remove* the post from your home feed.
If people abuse this, block them. 🙂