as we all know, to identify a team member scratch is used “*”, but a situation that someone creates an account called “#scratch12345& *” what happens?

You can only put letters of the alphabet, numbers and the “-” and “_” symbols in usernames. No other characters such as “#” or “*” can be used in an account name. Also, keep in mind the * in a Scratch Team members username is not actually part of their username. It is just to say that they are part of the Scratch Team. For example, Paddle2See's profile says “Paddle2See*” but the actual account name is “Paddle2See”, as seen in the URL https://scratch.mit.edu/users/Paddle2See/