Not that my opinion counts for much, myself being a cis hetero white male (AKA "skinny white boy from rural Texas"), but I thought I'd add a little to the discussion.
First, though I'm sure I've had numerous slips which I account to all my meatspace friends being male (a situation brought about from the fact of like-aged individuals in my area being 90% male [and that I don't really consider my classmates "friends" {it probably bears mentioning that I never attended public school until college}]), I try whenever I can to refer to people as "they" or by their username, because this topic has been brought to my attention since first entering into this corner of cyberspace. I'd like to say Keeper was instrumental in this, and in helping me becoming more mature since I joined as a teenager.
I'm sort of on the other side of things where I feel like just identifying as nonbinary (as I do--not that anyone noticed probably because again no one actually looks at the profiles for that probably
) is just half the battle, since that doesn't necessarily keep people from just referring to you as "he" out of simple lack of knowledge of what your preferred pronouns are. (This is all ignoring the fact that I'm still not totally sure how I want people to refer to me... >_<)
I can definitely see the importance of asserting a non-Cis identity though, and I wouldn't want to erase that.
*raises hand sheepishly*
I don't think I was even aware that there was a gender selection option in the profile page. I only just now looked at Keeper's profile to see that, yes, in fact, there is, and, yes, in fact, he doesn't identify as male or female. I don't think it would be beyond credibility to assume that 90% of our userbase hasn't checked anyone else's profile for that purpose, either. I would be all in favor of adding a gender as well as preferred pronoun options to the user sidebar. I would assume it would remain blank unless users altered it.
I hope it wouldn't be too difficult to add options to it later; if it is very easy it would be nice to have this up and running as soon as possible and make little tweaks later like adding words or gender identities down the line.