I am not jumping on the bandwagon to accuse someone of cheating here, especially as I haven't played mossgroup, and I have not studied his past games so I am giving him the benefit of the doubt, but I feel I need to get my two penny worth in here regarding cheating as a whole.
If a person is cheating in this way then thats fine by me, I don't care enough about correspondence chess ratings to get all irked about it. The only person really getting affected by this is the person conducting the cheating.
And if people also want to cheat by using computer software to take there moves for them, then thats fine by me too, I have been playing against computer chess programs for 20 years now since my first chess program on the spectrum, and I find them pretty predictable, even the quite powerful ones. So if you want to play me using mechanical assistance, fine, I probalby beat you 8 out of 10 anyway.
The type of cheating that I hate (if you call it cheating) and have experienced recently are the ones that play mirror chess. Scenario, I was playing against an opponent, I am black and I destroy this opponent who has a considerable lower rating. I play the same person and I am white and every move I make is mirrored back by that opponent. I know this is not technically cheating as it usually is a suicide style tactic and black ends up losing anyway. But I joined RHP to play chess and have fun, this is not my idea of fun, especially when you are waiting for days just for an opponent to mirror your move.
I don't mind any cheating as long as it does not affect my fun and enjoyment of the game.