I just tried to pick a vanity url for my public CV, and I find that it auto-saves too quickly.
I wanted a vanity url like "john-doe". But if I don't type it fast enough, the auto-save of "john-" removes the trailing hyphen, so when I continue to type I end up with "johndoe".
Note: It is not the case that a hyphen is not allowed, because if I type quickly it accepts "john-doe" just fine. It just doesn't allow a trailing hyphen.