My favorite part of all this is that the ACD canon is 95% first person stories written by an unreliable narrator (at the very least Watson fudges names toward protect identities, after all.) Let's look at this from a Watsonian POV: if there WAS a sexual relationshkp between the two of them, would Watson in a million years write about it? Especially since this is around the same time Oscar Wilde's going on trial?