I played an old teacher of mine on this site. This teacher is expert playing strength and class A rated USCF. He offered a draw in a game I thought for sure I would lose. After the game he sent me a trophy of strikingly strong play; I guess he though I had improved since we last played. I actually have improved during the 4 months between that game and the last game because of intense studying and chess club.

Yeah I think he could have played for the win.
6... Nxc3 I don't really see a compelling reason for, as it strengthens his center at a cost of development for you.

9...Qf6 seems a little odd, I can see you want the option to castle queenside, but it doesn't really have a threat and puts the queen on the b2 bishop line.

15...a6 doesn't seem to have any point at all.  You gotta push your attack quickly, opposite castling structure means staying ahead on tempi is huge!  I'd play for h4 as soon as possible, although the immediate h4 e4 Qg5 g4 slows you down a bit.

maybe instead 18...hxg3 19. fxg3 Qh7 would have some pressure?

22...Qc5 is just a bad move, you let him destroy your pawn structure, and you were on a verge of breaking through, where your queen would really help.  Qh3 looks pretty good to me.

You played a decent game, with only that one little combination costing you a pawn.  I think you really had the potential to win if you hadn't traded down into a worse endgame.

Hmm... I'm not entirely sure why he would offer a draw here, it appears to me that White holds all of the cards in this position... Either way, a pretty well-played game. I figure White should have kept his Queen via Qc7 or something along those lines. You know, put loads of pressure on your kings and all that.

Note, Nimzorevenge is not a class A player, he is high class B. (Class A starts at 1800, Nimzorevenge is rated in the low 1700's.)

Note the second, Would you care for a game?

 I was for sure he was 1800 rated. Also your ceaser told me he was expert at one time. Yes, I will play you.

 when I first reviewed the game I noticed almost all those mistakes, and I still have no idea why I played 15....a6

Can't help but notice that the game was unrated... not that I would play any differently.