I personally frown down upon them, but I don't always directly remove them. Especially if its a one-off case, I don't think its worth the effort (albeit very small).
In the first case I think we should simply point out to GetFitChimp that we'd prefer it if he left it out of his answers in the future.
In the second case, I believe that user simply copied GetFitChimp, since I never see him do it on SO (yes I checked, sue me).
In the last case we had an inexperienced user, who thought it was polite to add it, which is probably the reason people use it in the first place.
So what to do? Leave a comment pointing it out that they can leave it off, since its unnecessary. While editing it out, you can leave a comment saying the same thing, which is probably enough in the case of a drive by user.