I'm not currently doing this ... Your second paragraph is correct. This modification is just a quick hack so that if you download a playlist, then download it again later, it won't download the same files twice. I think just leaving out files that have already been downloaded is not exactly what we want to do (I think it will be confusing to people, and will not work across download sessions), rather I think a little bit clearer solution would be implemented like the subthread of this discussion that Tony and I and talking in now.