That is very true—Keith sets himself up as the cynic who doesn't have any feelings or care about/trust in love at all, but he's really a pretty decent person all along, besides the falsehood of the Don't Believe in Love act as revealed by his feelings for Ewen. There's that line earlier on about the 'careless, loose-living' London gentlemen whom Keith compares unfavourably with Ewen—and I suppose that also contrasts Keith himself with another kind of (moral) non-caringness.

Also, I completely agree about the suppressed/distanced feelings breaking through being fannish catnip. Ah, Keith :D

I don't know what to make of Captain Greening's feminine looks/manner?

I was wondering about that too, but had the same thought that most of the villainous characters are more masculine. (Trying to think of relevant examples from Broster's other books, it occurred to me that Raoul, of course, can pass for a woman in appropriate clothing—but we are also reassured that his face 'had no suggestion of the feminine about it'. Hmm.)