...is
Wizard 101.
It's quite possibly the cutest game ever that still has enjoyable gameplay. (Except for maybe Fur Fighters on the Dreamcast. That was Halo with fuzzy animals.)
And, like all my favorite games, it's free.
However, the chat system is super annoying. For one thing, many of the players are under 13 and can only use canned chat. Everyone older than that may use general chat, but the filters are severe and edit out anything not recognized by the system's dictionary, including many common emotes and abbreviations.
In some ways, this is a good thing. It eliminates profanity and encourages proper spelling (HOORAY!) in one fell swoop. Since the game promotes itself as family-friendly, the heavy filters and restrictions make perfect sense. And players 18 and up can choose to enable Open Chat, which is strictly monitored but not filtered. However, you can't enable Open Chat unless you pay to subscribe to the game. And damned if I'm going to spend money just to be able to say damn.
You can't really evaluate Wizard 101 on the same terms as Dungeons and Dragons Online, which is always full of lively dispute about stats, rolls, classes and saves. And you can't even compare it to the awkward sexual tension that often characterizes common chat in Perfect World.
Let's just say I don't play Wizard 101 for the scintillating conversation or social interaction. I play it because it's fun, cute, and totally addictive.