I agree with luzula about the implausibility of reading Keith as straight—but I especially like your point about Ferrers insofar as it means Keith's non-straighness isn't only apparent in his slashy relationship with Ewen, but is a consistent part of his character. No, he does describe Alison as good-looking, but he definitely isn't as glowing or appreciative about her physical appearance as he is about Ewen's!