If 10 or 20 members report these posts as plagiarism in the right way (with the source), then I don’t see how anyone could ignore it.
I don't think "voting" by sending in many reports helps.
It may not always help, but I know from experience that some of my plagiarism reports only got handled when someone else reported the same post. If 10 people with a high reputation agree on something it will have a much bigger effect than if there is only one member behind it.