And I think the real problem is:
That policy is, in fact, a bad policy for non-RP servers, because a lot of people playing MMOs don't care about immersion and don't expect any. But the solution was not "this policy should not exist". It was "this policy should be specific to RP servers". Because on RP servers, it serves a big point and is a big deal to many people.
Here's the thing. If they'd actively enforced the naming rules, I don't think anyone would have quit over it. People don't pick funny names because they're deeply attached to their character concept which only works if you allow the funny name. (Well, not in a fantasy MMO. Obviously they do in City of Heroes.) But if they take that policy away, of course people will quit over it, because without that policy, RP servers are pretty much useless. They're not offering you a reasonable expectation that the game world will not be full of lolcats and 4chan memes.