About Conner, one could argue both ways. Either the way you did or "Conner was taught in secrecy, so he knew that this was a really dangerous and forbidden thing". Even a child understands that if you must hide something, it is considered bad by the outside.
Regarding the pressure I disagree. People are different and for some, feeling like an outcast or not living up to somebody's expectations (especially if you adore that somebody) is just as bad as a parent dying.
And for a kid to be especially ambitious, usually it was raised in that fashion. Keep telling a boy he shouldn't cry and be strong and he will struggle with this for the rest of his life. Keep telling a girl she must be quiet and submissive and she might never be able to stand up for her rights.
Also, it's easy to disregard something as obviously wrong/stupid/foolish when looking at it from the outside. Smoking, drugs, alcohol, too much unhealthy food, no sports, not enough sleep; so many wrong/stupid/foolish things we all do despite knowing better. Seeing how we can't even be "clever" in such tiny issues I find it hard to judge things I can't even imagine. If I were Dalish, raised with this expectation that I must become a strong hunter one day (can't even get the girl you want if without presenting your prey), living with this fear of being enslaved by the oppressive majority, and always hearing how everything my people ever had was lost.... I dunno. Maybe I would also want to get this relic so badly that I'd do something wrong/stupid/foolish. I just don't know.
I think both deserve understanding. Not the kid failed, but his clan for not teaching him better. And I guess that's why Solas approves of you being harsh. It's not to much about the boy, but showing the clan very clearly what happened, so they take better care next time.
I agree that there is something to be said for being harsh with the clan for not teaching him better and I would say that Solas' approval most likely stems in this in truth.
As for disregarding things, I've been on the receiving end of that sort of dismissive callousness about my problems for a very great portion of my life and I know all too well that different pressures do not diminish the suffering they might cause. I did not mean to imply that they can even be equated in terms of relevance nor that we can fully understand the situation just looking at the surface of it; however, I did not base my opinion on the source of his pressure in and of itself really, rather on the tone of what he left behind. He didn't sound desperate, he did not approach his self-imposed task with humility or as an attempt to reach out, he sounded like he wants to just be better than anyone else because he can. That to me says that he was reckless and yes, deserving of pity and sympathy, yet we were speaking of how these two cases compare, not about the value of the elements of each of them.
Perhaps the clan could have done better to notice his feelings and to instruct him, but he also might have just as easily been on a teenage ego trip for all we know; the reason why Connor is easier to sympathize with is because his plight was an obvious tragedy from the start where it's difficult to blame a child trying to save his father. Plus, it helps that Connor is pretty much fallen in on himself from the guilt of what he wrought - he has humility enough to realize that he is neither above reproach nor is he exempt from the responsibility of what he had done, regardless of his intentions when he did it. When pitting that against the single letter we find on this poor boy, we don't get much except that for some reason he thought this was a good idea - and we know that his sister at least tried to reach out to him by the way she spoke of him.
Again, I am in no way trying to diminish what happened to the boy, but that does not change the fact that what it looks like is a perfectly preventable tragedy that someone should have been able to see coming and stop in its tracks simply because it seems like something that one could easily have remedied with the right kind of attention given to him. Of course, the world doesn't work that way and we do not know of any mitigating factors apart from a vague idea of what he was up to and why. So, we can only judge this situation based on such meager information and when weighing these two cases, I still would say that the intent matters; it's not a question of the validity of a particular kind of anguish, but the actions you choose to make in reaction to that anguish. Even were you to save the world by stepping over a line here and there, that doesn't change the fact that you can and must pay the price for it, so ultimately it comes down to the question of whether or not it was worth it. Besides which, one can be perfectly foolish without that diminishing the need to show compassion for someone and to try and help them, these things shouldn't be mutually exclusive.