Does this really need saying? Oh, probably.
A small for-the record, which seems to me so obvious I never thought it would actually have to be said, but…
COSplay is its own artform, and its own branch of fandom.
I love it when I see people, of any gender, in well-done or enthusiastic costumes of characters that I made up, whether from comics or from novels or from films or from TV. (It’s one reason I reblog them.)
I don’t believe that anybody in the costume is under any obligation to have read my books or comics, to have seen any of the films, or to like the TV show in question. I tend to assume that if you’re dressed as (say) Death you probably like Sandman, or if you’re dressed as Idris you like Doctor Who, or if you and your girlfriend are dressed as Crowley and Aziraphale you are very probably Good Omens fans, because that’s the way things normally are, but it’s not always true and I do not take it for granted. (Sometimes people like the costume and thought it would be fun, sometimes they were roped in by friends to make up a set of the Endless, or whatever.) I’ve definitely had to reassure a few people over the years that I loved their costume and did not mind that they hadn’t read the book or comic it was based on.
I really love how far COSplay’s come over the last twenty five years. I think it takes skill, craft and guts to make costumes and to wear them in public.
So that’s what I think.