The specific dialogue is-
Kieran: Mother never told me the Inquisitor was an elf.
Inquisitor: That's not such a terrible thing, is it?
Kieran: No. I just don't know why your people want to look like that.
or
Inquisitor: The ears gave me away, didn't they?
Kieran: No. Your blood is very old. I saw it right away.
He's not necessarily talking about the Inquisitor specifically in either response, but more likely elves as a whole. If that's the case, he's implying that the ancient elves might have literally chosen their forms somehow. That's a good thing for theories where the elves/the elven pantheon started out as spirits like Cole. As for the very old blood comment... he could simply mean that the elves are an ancient race and he could sense that in her blood. Or the Inquisitor could be a direct descendant of a specific bloodline. I dunno, really.
I had a weird thought. Either the Lavellan clan is somehow more "pure" than other clans, or perhaps... well, there are ancient elves still around. Who's to say someone didn't slip off and find love among the Dalish? Yeah, it's too Sue-ish to be true, but if it turned out to be true I would so giggle.
So I just finished "The Masked Empire" (binge reading FTW my poor eyes), and I am 100% convinced that Felassan was Fen'Harel. I have no idea if he was just body-surfing or who/what "killed" him, but the clues about his true identity are just too flipping numerous to mention.
I thought that too, at first, but then... no one recognizes him who should, if he's the same person. I don't think he takes over bodies, so that seems unlikely--I think Solas is, physically and mentally, Fen'harel. Granted, Felassan kept his face shaded under a hood most of the time, so it's possible that people just didn't see much of it? And we know that Solas can remove vallaslin, also. However, even so, you'd think that Briala, Gaspard, or Michel de Chevin or, well, even Gaspard, would recognize his voice, at the very least.
I really wish we'd been able to meet Felassan; he was a fascinating character. If he'd turned out to be Solas/Fen'harel I suppose we would have... I just don't get that impression. Felassan seems to be serving someone, and he failed them, and so he was slain. Whether he was a slave or just a follower, it isn't clear, but I believe he may have been a member of a group of ancient elves separate from the Mythal worshipers. In other words, the Sentinels are not the last bastion of immortal elves. He made it clear that Briala would not like his clan.
Also, if Solas were Felassan, I'd have expected him to have far more empathy and sympathy toward Briala, even though he may disagree with the specific path she chose to take. Felassan had a very close relationship with Briala. I doubt simply parting ways with her would have changed his opinion so drastically as to make him suddenly distant from her by the time of Wicked Eyes, Wicked Hearts.
On another note, has anyone tried playing a Lavellan who totally promotes him/herself as the Herald of Andraste? I would love to try that, and then tell Solas I'm doing it so they don't kill me, or something. Maybe play a character who's more of a trickster than Fen'harel, in every possible place I can do so. The Game? Oh, certainly, I can play it... and I will win it. If Orlais falls, so be it. I like Ferelden better anyway. Fewer masks, more straightforward.