Actually the answer is “no” (depending what you mean).
The Terms of Service state that you are not allowed to receive assistance during a ranked game. Any specific comment about moves in the game in progress, and especially exploration of variations, is likely to lend assistance and is not allowed.
You are allowed to say “Oh, darn, that was a mistake” or “Oh, good move”, even though technically even these can lend assistance. Everyone knows that players will acknowledge each other’s moves, this is just polite conversation (*).
However, you are not allowed to say “Did you see that K10 would have been better” or “I was afraid of this variation”.
Put these things in Malkovitch, so they appear to your opponent the moment the game finishes.
*: My personal experience is that every time I do this, I regret it later. Either it wasn’t actually a mistake and I spot that after I said it, or some other reason to regret commenting on the actual state of play. Personally, I have found conversation during the game is best to be about non-game entirely, but that’s just me.