This is a very, very minor issue, but I happened to use an auto-generated password for my account, and naturally, I wanted to copy/paste it in when the game prompted me to log in.
It just so happened that I forgot I had just copied a 3803 character segment of a word document a few minutes after, which I pasted in its entirety to the Password field.
Now, I could have just reloaded the game, but I wanted to try just deleting that segment first; using ctrl+backspace, using ctrl+shift+backspace, selecting with the mouse, using shift+arrow keys, etc., and those didn't work.
This is very obviously an extremely niche and minor issue, but I'm pretty sure no one is running around with a 4000 character long password, and it wouldn't hurt to put a limit on there, say at 80 or so characters. Well, maybe there is someone out there with a 200 character long password that would be locked out of their account with such a change, but I find that unlikely.