A strange comment. True, this position could be reached by 1. e4 d5 2. e5 g6 3. d4 Be6, but neither 2. e5 nor ...Be6 is very typical of the Scandinavian. I'd just call this "unusual opening".

I think this is a little premature, black (and white) should be concentrating on development atm. Better was 5...Nxf6 and 6...Bg7

True, but black is not developing either. Too many pawn moves are dangerous. See my annotation "1st Reti System mini-tournament" neilskye v peteywheatstraw

Continuing development was really called for here, namely 9.0-0. Black has rather seriously weakened his K-side, which ought soon to be exploitable.

black's premature wing attack lacks development or piece support and leaves the king vulnerable. I would have continued to develop, and tried Nd2 followed by 0-0-0, then exploited the weak kingside.

Usually it is well to wait until it is pushed before making this kind of retreat, bearing in mind that you do have this defence available. However, White really ought to encourage Black to advance the g-pawn, as after ...g4; hxg4 Bxg4 White will probably find the h-file more useful to him than the g-file is to Black. To that end, I like 10.Nbd2, with thoughts of castling long, then attacking the K-wing.

I still like Nd2 followed by 0-0-0. If an attacker opens up lines in a premature attack, the defender gains the advantage.

I agree with dmaestro on Nd2. Maybe even without having to castle until late in the game. He's rather snug where he is, while the black king is opening up on all sides. Nh2 was a little too passive, though. ionadowman is right that it's wiser to wait for him to try to kick your knight out. As ion pointed out, the kick-out attempt would have been to your advantage anyhow.

I think 11.Nbd2 was better on general grounds, followed by 12.0-0, or 12.Qe2 (this could even be played a move earlier) threatening 13.(12.)Bxg5.

Nd2 develops a piece.

Black has serious weaknesses on the light squares - for now at any rate. But White has lost quite a lot of time, so Black might be able to make good a lot of the damage before White can exploit. I would almost certainly castle here if I were White, then bring the queen's knight out to c3.

Black wasn't worried about the check, they are trying to provoke White.

By now Black has the edge. White has a lot of time to make up. So does Black, but the knights will be fully active in two or three moves...

Black has provoked White into an unwise retreat and now has the initiative to justify the previous moves,

I think move 14 was a good opportunity to reverse the passive Nh2. Nf3, with hopes for Bd2 and Bb4. If 14. ... g4 15. hxg4 fxg4 16 Ne5. Good outpost for your knight, and at worst removes the threat of the dsB on your d pawn.

Black leads in space and development at this point. Consequently, white should be looking for ways to exchange off some pieces. I quite like 16.Bg6 and 17.B(x)f5 which exchanges LSBs (and possibly queens) and gives white control of g4 so you can activate your rather passive knight on h2 aggressively. That would also denude the BK of some defensive resources so you could follow up with O-O and Re1.

However, once again a bad bishop for White, while every Black piece can be active on the King side for an attack.

Black, for sure. One plan here (for Black) is to seal off the Q-side (...a4) and then go for an all-out attack on the other flank. But there is something to be said for maintaining the tension at b4-a5 for the moment, and getting the BK off the e-file with ...Kd7.

Black has the initiative and White can only defend.

Both sides have good potential, but yeah... black does have a slight advantage (helped mainly by that beautiful knight outpost). I have a bad feeling that your opponent might underestimate that knight's value, though...

The position is a bit closed up for me to like either side! I would say black is a bit better, but white has chances too. White should look to liquidate the black knight on c4. Perhaps Rfe1, Bf1, Qc2 is useful.

  Repeated moves like those are the futility of tightly closed positions. This is why I like to have at least one open file in my games.

Even with a horribly closed position, passive moves can only help your opponent as they give him all the time in the world to build up behind attacking pawns