(re-posting old content for the sake of gaining more karma,etc)
Some members of Bitcointalk have a similar approach towards Merit.
Don't know about Reddit rules that much but I think they should have some rules.
But over here on Bitcoin talk if you reposting old content it would be regarded as plagiarism unless you put reference or quote.
So rather than making a thread for merit whores or so you can report to the moderators if you think they reposted an old content