I don't want to know your gender. I don't care. It's your thing. It's non of my business, and it makes no difference to me whatsoever.
If I do want to know your gender, then things between us are starting to become intimate.
To sum things up: I would say it's rude if someone shares his gender identity with me without being asked. On the same level as if someone shares his/her dick size without being asked.
We are in a society that demands special treatment and we've become so afraid of offending people.
To the offended - Don't be, assume the best of everyone and things will be fine. The problem starts when people are offended and they require special treatment. Malice, racism, segregation and other forms of abuse is not part of this clause. Those are universally inexcusable.
The way this decision and surrounding information about the new CoC can be read, is that it's no longer about avoiding misgendering people. It's about having to pay fealty. Writing around gendered pronouns means weaseling out of having to make a stand on the issue, which labels you as the enemy.
There is a perfectly good third person pronoun for this situation. Some might decry it as a neologism, but I suggest it has been around long enough and has firmly entered the language:
"OP".
But of-course I don't think sharing the name is rude, it's a basic personal reference. It would be rude if it's followed by "I'm straight" or "I'm a woman". As for pronouns, in most languages, you can know the [grammatically] correct gender automatically from the name. And if you don't, most grammars have middle or neutral gender, so that can be used. The issue here is that we shouldn't bother other people with our gender identity.
It’s no more rude than having baby pictures or a wedding ring or a cross around your neck. These are all examples of intimate disclosure which have little or nothing to do with some idealized cold professional relations. People wear their identity in many ways and the rest of society is perfectly okay with it.
But what if you can’t? Or there aren’t enough context clues to determine this? For example, my username contains my name in it; do you have any idea what my gender is? Or what I’d I had a “gendered” name but actually had a different identity personally?
But really the problem is that gender comes up in conversation a lot more than orientation. You can get a lot further in a conversation without the latter than the former, so some people see it fit to frontload that information.
I disagree that personal gender is often relevant in that kind of discussions (SO, or similar general topic forums), and when it is, then it's perfectly normal to share it. The same goes for dick size. But why to mention it if not necessary?