It's been rightly pointed out to me that it would be counter to my position that you own your content if we didn't allow for attribution to be removed. This morning I was thinking of it from the perspective of a user that left, but wasn't determined to erase all history of interaction. It's my assumption that there are some. I think the best way to do it would be a stepwise option. You can quit, your name gets a strike-through, or you can peace-out and your attribution is gone. I'm not coding anything for the next couple of weeks as it is. I should have given more thought to the matter before deciding anything. I'm sorry about that.
After reading everyone's comments, feedback, and use cases, I don't think you need to change a thing. My reasoning behind username/content permanence was that people should be held responsible for what they say and do online, just as they would be in the real world. A "staged exit" like you propose would not dissuade the trolls from trolling, because they can still disclaim responsibility for their actions. It would only make a more complex system, with minimal practical utility.