I don't find the semantics all that different, and certainly on OMNI P/R, nobody's going to suddenly start finding the unhelpful political chatter helpful because someone clicked on it.

Even if labelled "helpful" or "thanks," I don't think many users are going to be so unsophisticated as to automatically assume content is more valid because it got what are in essence "likes," but if other folks think that it's confusing or misleading then that's a good argument for using a more neutral term.