I think Paolini should stick to writing teenagers, personally, and not try to pretend they're "mature".

I agree. When he tries to write adults he just ends up making them so painfully immature and childish that it's not remotely believable that they are adults. Okay, there are adults in real life who are super childish, but when the entire cast is like that and they're somehow entrusted with commanding spaceships and leading armies and whatnot, it stretches suspension of disbelief well beyond breaking point.

This could work if it was established that Kiragon was traumatized as hell, but we all know how good Paolini is at writing that.

ie not at all. For feck's sake, when you're super upset about someone dying traumatically in front of you you can't just switch it off at will. That's not how emotions work, Chris.