I'm afraid I don't have anything too useful to say, here - I was too busy reading the story to want to be in editor or critic mode. I didn't notice any technical problems anyway, though the "up your geek" card might have been played a time or two too many. There was only one of them I didn't recognize anyway, but by that time it had become irritating to the point I didn't care enough to look it up.
I do think MC is being a little hard on Celestia at the end - she's not horrified at him per se but by the amount of violence done to him recorded across his body. If she feared exactly what war might mean for her little ponies and thought she knew what she was asking him to take on in their place, now she knows and is probably feeling really, really guilty about that request, but still not so much as to release him from the agreement and not shield them from as much as his hard-earned experience can because she hates the thought of even one of them suffering the same way even more, and feeling like even more of a hock for that. I predict a highly-contrite sky-mare appearing somewhere in his near future.
I do think MC is being a little hard on Celestia at the end - she's not horrified at him per se but by the amount of violence done to him recorded across his body. If she feared exactly what war might mean for her little ponies and thought she knew what she was asking him to take on in their place, now she knows and is probably feeling really, really guilty about that request, but still not so much as to release him from the agreement and not shield them from as much as his hard-earned experience can because she hates the thought of even one of them suffering the same way even more, and feeling like even more of a hock for that. I predict a highly-contrite sky-mare appearing somewhere in his near future.