They do. After I deleted all my comments, using automatic tools (that replace the text) and manually, they keep recreating them. In fact, this might sound a bit like a conspiracy, but I've noticed all my comments that do come back are the ones that people find coming from Google.
So everything is deleted, then some user searches Google for a solution and my comment was the only one, as soon as they click the post, my comment is back and shows up in my account. The original comment, not even the modified version that should've replaced it.