Actually many of them maybe fake but if Satoshi should come now nobody will believe that it's the real Satoshi, because of alot of people impersonating with Satoshi. And for someone to believe Except it's the people who meant Satoshi when he is in the forum will know his writing style to be believe that it's a real Satoshi.
They are all fakes without any doubt, except for those people who believe in fairy tales and don't know that Satoshi has his own account on this forum - all he needs to do is prove that he is the real owner to the admin and he will get access to his account on this forum. The style of writing is the least relevant here, because someone a little more intelligent can very easily copy it, which does not prove that it is the same person.
I would solve it in a very simple way, anyone who appears on the forum claiming to be Satoshi would be given 24 hours to prove it or be permanently banned - such members have zero value for the forum.