There's a small cost to the confusion caused by your name leading readers to assume (with hopefully low confidence) that you're female, and there's a small cost to the confusion and effort required to actually change your username and update references to the new username.
I'd say that "shut up and multiply" says that here, on LessWrong, the cost of the confusion is VASTLY less than the cost of the effort you'd have to go through to sign up for a new username and explain the situation. So, Utilitarianism says that you should keep your name for The Greater Good.
The key here is that it's not deceptive - you're not intentionally misleading people, nor are you allowing a harmful confusion to persist. You're doing nothing harmful or immoral, there's just a tiny bit of confusion.
So, my current username often reads as female. This is not intentional, and I am not female. Some on IRC have pointed out that this username could be considered misleading or deceptive. I have no real attachment to it, but I do have a few articles that I've been discussing and planning on posting here, and I think it would be confusing for others if I changed usernames, making it difficult for people to follow the genesis of certain ideas. However, I also don't want to mislead anybody.
Therefore, I pose the question to the community: is my current username deceptive or otherwise misleading, and should I change it?