Yeah, it's considered cheating here. Probably a warning and maybe a forced adjudication in this case.
Copying moves in online chess - is it fair?
The main line of the Caro-Kann advance variation is 4 Nf3 (1 e4 c6 2 d4 d5 3 e5 Bf5 4 Nf3).
The side lines in the order of incidence:
4 Nc3 4 h4 4 Bd3Meantime I informed my opponent about this situation and he moved by his own mind, so the problem is solved. Anyway it is an interesting question and I asked support to comment it.

No discussion of cheating in main forums.
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Mod.
It has, in the past, been considered the same as getting outside assistance for your game.