I see the points you are making on leaving being a jerk move, but as I mentioned before, I have done that and that was based on respect and love for that person. He never felt he could reach me and he was right, no one ever can. I did tell him why I left though, but I'm not sure if that did anything.
I can't change that part of me, that would be wrong for the both of us. 15 years later, I think he hardly remembers me, I sure do remember him. I gave him the freedom of not always feeling frustrated and to get over it. I can't.
Edit; When I think about it, I'm not completely unreachable, it's just that I tend to click more on a intellectual level (not as in IQ but as "let's debate this till it's completely shredded to pieces), he was such a sweet, caring and emotional guy who just couldn't cope with me being a space cadet.
I once left someone "for his own good" and it was definitely out of love and respect. He was/is the kind of person who would end up miserable in my company eventually, either because he stayed who he was ( and we were very different people) or changed his values to match mine. He is happy now, as am I.
I do hope I am not offending you guys(gals), because I will say I've never been in this situation so I can't know 100% what it's like.
BUT there's a big difference between (RL) "We broke up because they would never be happy with me" and (fantasy) "We broke up because I'm an all powerful god and I just don't want to explain that right now".
When I talk about the trope I am mostly talking about it in the context of fantasy, or superhero genre, where the leaving is done because of the fear of some physical harm, or the idea that they couldn't "cope" with who you are. It sounds like both of your situations were based on mutual happiness--while it may hurt right now, in the long run you're both better off, and part of you both knew it (likely because your partner knew on some level what the deal was). But I don't believe for a second that Lavellan is "better off" without Solas. Pffft.
My gripe with Solas is that he doesn't even offer a reason for why it wouldn't work. I mean, this is a world with freakin' magic and monsters and craziness--at least telling Lavellan he had some unfinished business, that he had to go and go alone, but he might be back... maybe... That makes sense.
But just being like "No, it won't work" and disappearing is just not right.
Both sides of the argument come off as only letting one person's feelings matter, now that I look at it. It's either Solas' decision not to let someone get hurt for him that's denied or it's Lavellan's decision to risk getting hurt for him that's denied. It sucks either way. It's kind of a no-win situation.
In a way, yes, it's only allowing one person's feelings to matter. But the point is, in the first case (leaving for their own good) you are being selfish and only allowing your feelings to matter. In the second case, you're letting them choose, thus putting their feelings above yours (not selfish). Also, consider that in this trope the person doing the leaving often wants to be with the person anyway, but thinks themself selfish if they stay because their partner might get hurt. Yes, it's selfish if you don't tell them the truth, but if they go in knowing all the risks, then you can't blame yourself (even though of course you will anyway).
Bleh sorry I didn't mean for this topic to go so crazy. I just wanted to point out the hypocrisy of how "leaving for their own good" is not the selfless act most media makes it out to be. I'm not saying that the opposite is always rainbows and unicorns, or will end happy. I'm just always an advocate of letting someone make their own choices, this trope has always annoyed me.