I've seen several instances of new users posting links to scanalation sites for manga or full anime episodes. This is (as far as I can tell) not allowed here. The canonical reference for this is How do we deal with copyrighted material on our site?, which says that moderators aren't responsible for policing copyright violations (which I agree with).
However, it also says that links to fansub groups, scanalation sites, etc. for the purpose of sharing the illegal content are clearly out of bounds, and I would argue that they also make our site look less professional. This doesn't apply to embedded images, links to short video clips, or legal streaming sites. When a new user posts such a link in an otherwise good question/answer, I'll typically edit it out (possibly replacing it with an image or quote if there's a reason to do so) and leave a comment to the effect of "please don't post links to illegal sources for anime/manga here", which hasn't caused any problems so far.
However, it's also common for new users to leave such links in comments. A recent example is here. In these cases, I leave a comment telling them the same, but there's not anything I can do to get rid of the links. If the user deletes it themselves, we're all clear, but if that doesn't happen, there's no practical way that I can enforce our no-fansub policy, besides a custom flag for moderator intervention to delete it.
So, with regard to such comments (containing material which clearly violates our policy on fansubs and scanalations), which of these is the best course of action?
- Leave a comment informing them of our policy, and if they don't delete the comment then do nothing.
- Leave a comment, and wait some period of time. If they don't delete it, then flag it.
- Leave a comment, and simultaneously flag the post.
- Something else