there are a variety of reasons why it works this way - a lot of posts would break if we didn't allow you to position your own read-more. i think there are some ways we could find a good middle ground, though. for now if someone were to bomb your timeline with the entirety of the bee movie script, you could block that person and give the timeline a refresh.
InvisibleUp
A friend of mine made a post on https://cohost.org/abcdefg2?page=0 to demonstrate this. Ideally you should not be able to "bee movie" or "do you love the colors of the sky" bomb people's timelines.