I see that the reason my Goujun always feels vaguely OOC to me is that I've never written him seen from the standpoint of an admiring inferior. Goukou and Goushou are older brothers and see him as their junior. Gouen loves and appreciates him, but Gouen has such a good conceit of himself, and their basic characters are too different, for him to want to model himself on Goujun. Tenpou in some part of his soul reserves judgment on both Goujun and, I think, everybody: or rather, as both the Gaiden and lebateleur's fic suggest, Tenpou doesn't give priority to his personal attachments even when they exist.
Yet I feel the manga presents Goujun from exactly the standpoint that no particular character expresses. For five years we've seen him only in his dealings with Kenren, who can't stand him. Yet we have the idea that he's an honourable man, an efficient soldier, and a good commander: someone fundamentally trustworthy (where I, at least, wouldn't trust Tenpou as far as I could throw him) and basically admirable.
That doesn't come entirely from ironic juxtaposition with the only too-human (if I may use that word) Kenren. It comes I suppose from the fact that he springs Kenren from jail, and that he seems at least partly in sympathy with Kenren's views. It's not 'Next time think twice before meddling in things that don't concern you;' it's 'Why the hell didn't you go through channels? We could have gotten Nataku relieved of the next mission if *I*'d been the one suggesting it.'
Military mentality, is Goujun. And military mentality is foreign territory in the kind of manga I read. It's also the most insidious kind of cultural trap. You may argue that soldiers are soldiers the world over and in all ages, but I'm just not sure. I know there's a significant difference between the American and British ways of leading armies, and if cultures as close as that can differ, what will we do between east and west?
In any case, my own default for armies is British, and when I write military types I have to fight not to do it in David Niven's voice. (We never went to films when I was growing up. Never. There were four of us and my mother wouldn't let us go alone, but taking four kids to the movies- and us whinging rotten spoiled brat kids at that- was an exercise in masochism she rarely undertook. Nonetheless and don't ask me why, we all went to see The Guns of Navarone. I remember nothing about it but I think it must have been a kind of primal scene.) But I rather doubt Goujun is Niven in any of his roles. I should be thinking Three Kingdoms stuff, I suppose (observe the illustration on the top of that page) but Goujun seems even less Three Kingdoms than he does David Niven.