Platinum: I'm curious to know how you'll be tackling the problem you just said there. Since if it changes (string replace I guess?) something like "A user" to "A_user" and there's actually another use registered as "A_user" there'll be problem...
You are completely correct .. however, since it is only a string replace and not actually altering theusers account, it is livable .. in the case that both users were to join chat at the same time, the irc software that is being used will automatically convert the second user to join to something like "A_user1" and everything will continue as normal .. if for any reason you wanted to know who is who, I have included a "whois" button, simply select the username in the list and press it to expose the users connection info ..
I hope this is a satisfactory answer..