Re: Why is it even an issue on SE?
I'm not so sure about that. It's a Q&A site, it should be about the questions and the answers. There are plenty users where it's impossible, to know their gender/desired pronoun, if you address people directly it's generally easy to avoid (you use the username, and 'you' generally. Frankly, it's hard to think of a case where dragging gender into the discussion isn't horribly off topic. You managed to write the above post without any reference to gender. I replied to it, addressing you directly, without running into issues. I didn't phrase things differently, gender doesn't come in to play when speaking in second person.
Generally it only becomes an issue when talking about users other then the one you're addressing. Because in the third person gender is relevant. But there it's generally possible to avoid it by just mentioning the user by username, which is often a good thing for clarity anyway. So to me it seems pretty much a non-issue which can only be a distraction from the actual topic being discussed.