I'm fascinated by the #UX of post length. First 140, then 280, it forced all sorts of complicated editing techniques/threads to make things fit.
With Mastodon I've got 500 chars! Freedom! But I STILL run out of space, albeit less often. Now I compose my first draft, usually well over 500, and then edit it down to fit. Single posts just read easier and replies are simpler to follow.
I don't read most posts >3000 chars as they tend to ramble. 500 is a forcing function, the TedTalk of post length