FTR. I meant open a new account and not use the old one anymore. Not simultaneous use of two accounts. Did not mean to offend anyone.
I believe one of the big reasons why that still would be frowned upon is because a lot of ladies use Perb posting history as a form of screening clients. I'm not inferring that's this issue with this poster at all, but say someone who has a history of posting offensive material or rule breaking decides to create a new account to circumvent the safety protocols that ladies use. Or even just circumventing previous bans/warnings/whatever. While it is possible to do cross-checking of IPs with new accounts on most forum platforms its also very difficult to catch everyone, especially when most forums have moderators who work on a volunteer basis. If someone wants to change usernames out of boredom or preference a PM to Fred probably is harmless but don't expect it to happen especially when there's plenty of other more pressing issues to deal with on a daily basis.
I'm only speaking from experience moderating a non-related sports forum that uses a similar platform. Sometimes there are hundreds of new accounts to go through and it's just not feasible to make sure everyone is a user with decent intentions by checking IPs.