I can bet a vital body part that there would still be the same 1-2% of banned users asking the same questions even if they get a certified letter in the mail with a handwritten note from theymos explaining why they got banned.
Even if that was to be the case, members wouldn't feel the need to spend their own time looking for examples of plagiarism. The answer to the banned member would be: "See the PM you got" and that would be the end of it.
And I would not take you up on that bet, because you might be correct--but we'll never know unless my suggestion gets a trial period at least.