It's the old problem of large print vs small print
Why doesn't the bot use the user ID instead of the username? At least for the configuration, then he can use the username to verify the quote.
To be fair, I think it's easier to get the username right than the user id. People also miss their user id from time to time.

I'll probably add a check so /menu and /start is considered invalid and the bot asks again (I've seen like 2 other users with /menu and /start as their username

).