I suppose this may be explained somewhere, but I've been at a lose to discover it. Why do GTP coordinates not use the letter I? SGF uses I, or at least doesn't mention it explicitly (http://www.red-bean.com/sgf/go.html). Most non-GTP go board markups I've seen use I. Sensei's Library lists some answers to this question, but they seem fairly vague and inconclusive. Is there a real reason or is it just convention?
Chris