I know I've seen the occasional quoted post with nothing added, but I've seen that behavior on other sites where someone either didn't know what they were doing or it was an accidental post, so I didn't pay it much mind. Can't say I've seen a lot of those type of posts.
If the posts being discussed are not quotes, but individuals actually copying someone else's post and submitting the text as a "new" post - can't say I've noticed that either. If this is going on, that is definitely plagiarism and definitely against the rules.
I disagree with having a special forum to report such activities, as I've seen that done on other forums and they usually breed more issues than they solve. First it opens doors to individuals who feel it's "funny" to report random people who've done nothing wrong. Then the people who are reporting guilty individuals start being treated differently on the boards as they are seen as police/narcs, which usually leads to hurt feelings all around.
Probably the best thing is to raise awareness of the issue (as this thread has done), and encourage people to contact FC directly to report users that are habitually not "playing by the rules" so their team can pay closer attention to them when reviewing PTP entries. The only caution is don't report people who may accidentally post a quote without contribution on occasion - be sure the behavior is regular so one does not accidentally report someone's honest mistake.
Just my 2 cents.