oldbus

Quite possible. An in-universe explanation might be the same as the real life equivalent of several people being in a room with some infectious with Covid - some catch it, some don't. Why? - a mystery. For the out-universe explanation - as Jaenara says: plot armour.

To be honest I'd answer, "No f***ing idea," to all of your questions (though I think they're reasonable questions to ask). Quaithe, unlike most of GRRM's characters, is someone who has got less impressive the more re-reads I've done. At first she seems suitably mysterious and offers intriguing hints to Dany. On re-read I tried to find out more about what her hints might mean and I keep coming away baffled. On my latest re-read (in company with Stephen Attewell's and Not A Cast Podcast's chapter-by-chapter analyses) it seems I wasn't missing anything. Rather than focussing on what Quaithe says, this time I am trying to focus on the impact that her statements have on Dany. However, I've only got as far as the early chapters of SoS so I've plenty to read yet. From memory, the hints seem only to make Dany a little confused, but don't really help her or especially hinder hew either, which makes the whole thing meh. Unless there's some kind of revelation from GRRM in Winds (and it is quite possible), I'm tempted to put Quaithe alongside Joffrey's catspaw as some of the less successful writing in ASoIaF. If you want a crackpot theory (no, I don't believe it), maybve Quaithe is from the House of Urrathon Nightwalker (she appears to be able to use a glass candle and we hear that glass candles burn in that house). This could make her bride fo Euron ;-)

Going for B though I think that is onlyu marginally more likely than A

Thank you for this insight - I've been wondering for some time about the oldest crypts being lower than the younger ones. In-world this makes no sense if they are dug/hacked out of the ground ("Well folks, we're going to put in some extra hard work to digs our crypt super deep so that future generations can build crypts about ours in a thousand years...") Out-world it makes perfect sense: in a story the deeper you go, the more mysterious things should be (and potentially dangerous as well). Up until now I thought I'd have to just accept the out-world reason and not look rationally in-world. But, with a cave system when you are trying to hide away from harsh winters (and anything horrible that came with those winters), you'd want to go fairly deep and it is legit to not occupy the shallowest cave.

While I would like to know more about it, I expect the problem is that it would prove to be a lot less fascinating if we did. Asshai is probably a place best left unseen directly, except for rumour and some Mel flashbacks

Reading this, one thing that I'm surprised has only just occurred to me now (others must have posted about it), is if Littlefinger has Alayne declared as a legitimate daughter of his and is therefore entitled to inherit his possessions. Littlefinger will need to offer a favour to a king/queen for that, but he seems very adept at doing that.