mod re-posts are not a thing that happens on pmc, the site is generally well policed when it comes to stolen submissions, but dont forget to report ones that appear on the site.

other websites however like all our favorites 9minecraft etc, you cant yourself do anything because you dont own the stolen content being used on those sites, the only thing you can do is not support the sites and get friends and family members to also not use said website

you can however report them to google to get the listing removed https://support.google.com/legal/troubleshooter/1114905

and report them to adfly http://adf.ly/abuse

and support/get involved in the stopmodreposts movement http://stopmodreposts.org/ (im lazy when i download mods so i installed their chrome addon so i dont use the naughty sites)

You could report it, and I believe that PMC is one of those sites where when it happens, it's also solved. I know there exists sites that are purely made to steal mods, but they won't listen to you, so the best thing to do is tell everyone to download from PMC or if the mod has orginaly been posted somewhere else, tell them to go there.

We can't really stop them until Article 13 steps in, in which case you'll be able to sue, or send anyone who copies your work a fine as long as they're in the EU.

Well, reporting is pretty much the only thing which you can do that actually has a good chance of having some actual impact. Complaining about it, though very understandable, isn't going to change peoples attitudes.

And there's even another side to the story, though this usually doesn't apply: developers who release a project under an open source license, then get upset when someone else forks the project and starts a new one based on the existing code only to end up more successful than the original project.

"Your mileage may vary" as is the saying.