Penggg
Yes.
Despite some insistence that I only want to cause a bunfight, I don't and am interested and can't post examples as I'll be TAAT'ing (can I?)
I've seen people asked their sex and I think I've asked too. It can certainly have an effect on both the poster's views as well as the way others respond and can be asked without offending or giving offence.
The thread I read most recently was a poster being a pedant (and a bit of an arse) but they were short replies with none of the markers you mentioned. Within a few posts, replies were along the lines of "ignore him", "he's bored", "he's showing himself to be a dickhead". It was a non-controversial, non-feministy thread and the gendering of the replies was nothing more than an insult.
There have been other examples more like Slarti's and MrsMud's examples where not toeing the line get's snide replies where pronouns change.
Battleax
One example, "I don't know why [username] keeps posting his BS, all his posts are being zapped now."
They were being an arsehole and deserved to be called one but there was no mention of gender or sex and neither was the topic gendery or feministy etc.
Russell
Firstly, I think I confused you with Pratchett. No offence.
The italics you used certainly felt like that you were insinuating I was a man or at least wrote like one. I guess that's the problem with written rather than spoken language.
I thought I'd addressed all points.