There are some browser extensions that will edit your comments and make them each a random a bunch of random words. I do not know how effective they are so I cannot vouch for them.

I know that if you tried to just delete the comment, the information would still be there but the username is deleted. Which is frustrating, I didn't know that until I had already deleted every post and comment, went back to make sure the job was done. It wasn't. I just came to terms that at least I wasn't contributing to their hub of knowledge anymore.