You are correct about Nine missing IMAP. In my post above I was looking only at the desktop/laptop e-mail clients.
I've seen that Nine's privacy policy is good. I've never tried it because it has no IMAP, and I need IMAP.
As for the conversations, - I guess, that's more Gmail-like style of presenting them. I understand why some people might like that, but I don't like that. The irony is that, because I didn't like how conversations were organized in Gmail, I was not expecting myself using Aquamail's conversations when Kostya first introduced them. I admit I was wrong.
Regarding the snapshot that you've posted (thank you!), I appreciate the offset (compared to Gmail). However, I wonder if that offset is done for multi-party conversations.
Also, this format works for 1-3-liners... What about conversations with screen-full messages?
Curiously enough, when the "chips" were introduced in Aquamail (Due to Gmail popularity), I turned them off. Did that in Gmail too.