Yeah, this thing goes both ways.
Sometimes people are really grateful, sometimes they are just copying the thanking process because others do it and they infer it is the polite thing to do.
By leaving a comment on a person's deviation, though, I avoid the need for the person to "spam" me (be it intentional or out of politeness), so he can still thank me if he finds it necessary. Since most people fave-and-run, such thing is not possible, and they are kind of asking to be thanked on the front page.