Many thousand things have been collecting within me for communication. Well, actually, just two subjects, each of them spanning two threads. But they both relate to 'Bother his Brains' as much as anything, so here goes.

Thorpes and money. I agree with all BarbaraB (a U-Turn) said about the suspicious timing of Isabella's big turn-around. It's further supported in ch18 (She wished Isabella had talked more like her usual self, and not so much about money, ...). Sooo, it's interesting that money-sensitive John is still talking in terms of marrying one Morland, when money-sensitive Isabella is going off the idea of marrying another Morland. It could be that he hasn't yet heard Mr Morland's financial arrangements for James, or that he sees something more promising in Catherine's prospects than in James's.