that's a very thin fabric for a top garment.... But I can see the writer is having fun with it.

Well, I suppose it *could* have been an indication that it was an extremely expensive shirt...!

"his warm brown skin had gone dull and worn." That looks like a modern view creeping in. Are we in the period where a sun tan suggested you were working class? Or could men get away with if they did a lot of hunting? A society woman certainly wouldn't.

No, that's the author fetishising the non-white love interest :p

(The improbably although not entirely impossibly half-Indian Marquis, who can be titled and yet discriminated against at the same time, à la Chevalier de Saint-Georges... she also has an immigrant flower seller character to boost the diversity so that her readers can further 'identify'.)