I still don't understand why we've got a 500 limit count but alt-text is sitting at 10k? Like, we could be just writing novels in the alt text, right?
@Kalshann The phrase "not thinking things through" comes to mind...
...though it kinda came to mind even before alt-text was a thing here. Like... why have a limit? Are we just copying (the network formerly known as) Twitter? Literally no other social network ever had a post size-limit that small (to the best of my knowledge).
Fortunately, individual instance-owners can change it... [coughs quietly] 
@woozle
True, though I suspect it might be erring on the side of caution for traffic? Or was done in anticipation of traffic? Not sure. You may be right.
I've not moved back to a small instance because I'm allergic to other people's drama and the first two instances went up in flaming drama so I am kinda hiding in among the herd of normies now. (Now I want a collective noun for normies?)
Note: This isn't me saying wah wah the alt text is too big - fuck you very gently with jagged glass. Alt text needs space for discription, especially for those who use it as their primary point of contact with visual stuff, that's a net good! This is just me being confused why there is such a vast (x20) difference between the two, ya'know?