Sam Gwynn, you are right, I reversed Christian/Atheist by accident. Shade says that he doesn't believe in God--which would seem to align him with atheism. Kinbote is clearly a Christian.
Jansy, when you say that Shade is ambidextrous, I assume you are referring to his calling himself a "bimanist." I don't think he is saying that he shaves (and therefore writes) with either hand. Rather, he is saying that he holds his sagging skin taut with one hand while shaving with the other (as opposed to the one-armed bloke in the shaving cream ad). Your comment has, however, made me wonder why I assume that Shade writes with his right hand. Is this stated somewhere in the text? As for the beard, I think you are mistaken that Kinbote does not always have one. He admires its "rich tint and texture" and in the faculty room scene the lecturer remarks that "King Charles wore no beard, and yet it is his very face," meaning that Kinbote does have a beard. I don't see any reason to assume that at this point it is a fake beard.
Sergei, as for what Botkin teaches, I was simply repeating the conclusion of others--based on his department chair's name, where Gradus looks for him in the library, and the subject of the lecture he was asked to give. All of these point to Scandinavian lit or language. But Kinbote/Botkin says (via Sylvia) that he was teaching Zemblan. I'm not sure why you would think this could mean math. If I said he taught Russian, wouldn't you think he was teaching the language?
MR