It's hard for us to prove he is using multiple accounts and bots to bump the thread.
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Can't mod /supermod see the IP? I was a mod time ago in one forum and I could see Ip from users.
How hard you think is to use a proxy for this ? I would not be surprised if there are bots with proxy support for this with some few thousand generic comments supplied as well.
You can confirm that bumping is going on there but there is no way to prove that it is him doing this. What is a competitor is doing this to malign his image ?