Declaring pronouns is like saying you want to be identified according to the social expectations of a certain group of people. I am not a group of people, and I DO NOT want anyone getting first impressions & making assumptions about me based on that.

It's like saying people should speak differently when "ladies" are present—I don't want someone acting differently or hiding their true self from me just because I say up-front that I'm a "she/her" or a "he/him". Identities and relationships are negotiated, not declared—and that involves the subtle art of politeness. In a professional setting, avoiding questions about the personal like who the fuck you sleep with. I don't want to care.

Even just putting these pronouns out there is a signal to watch what you say around such a peson because they take this identity stuff seriously enough to put it in a professional email signature. It's like bright coloring on a venomous animal. If I got two email replies for a business inquiry, and one of them was signed with a "she/her", guess which one I would avoid.

If you wanted to respond to HR sarcastically, say "YES! And we should all state our race & ethnicity too, so people know when it's inappropriate to use certain slurs!" ...I mean, think about that for a minute and what it implies.

FFS these people are idiots. It's like HR has never dealt with actual relationships with people before... then again maybe they haven't: they do call them Human Resources after all. Mindless robots.