i don't like client mute cause over time you might end up muting people you forget you muted, and despite them changing/starting being serious, you wouldn't be able to tell and thus stop thinking badly of them.
Ki's an example here: despite being a known habitual chat spammer, if he wants to be on a server he'll withhold acting stupid - after banning him once on centhra's for spamming, he didn't do it again and actually dueled and chatted normally on the server, despite his reputation.
had i client muted him and banned him immediately on joining the server would have had one less dueler to play against, one less player to make the server populated and engaging to be on.