I was just trying to create an account with a particular handle but kept seeing "This handle is already taken". This had me quite stumped until I checked the GET request for handle availability and realised it said "Reserved".
Looked through the code on here and, lo and behold, there's a ton of restricted handles lol. It'd be nice if that message below the handle field said "This handle is reserved/restricted and cannot be used" or something similar. Maybe you could link to a list of the reserved handles next to that notice as well?
fix is merged into main now!