Why do people write "he/him"? I see this (and "she/her") in the e-mail signatures of Americans I work with.

Has anyone ever declared themselves to be male in the first person, female in the third, and neutral/plural in the possessive: "he/her/their"?

The answer is multifaceted:

1) Because that's how people do it. Sometimes we all collectively settle on a standard that isn't the best, but that's just how it's done.

2) It allows for more easily expanding to multiple pronouns, e.g. "he/they" or "she/they", which indicate that the person is ok with "she/her/hers" or "they/them/theirs".

3) It makes it easier to state neopronouns (e.g. xe), by standardizing the form -- he/him/his is the same format as sie/hir/hirs or xe/xem/xems.

4) (My opinion) It feels more natural to say "he him" than just "he". "What are your pronouns?" "He." I dunno, it's a short enough utterance that it could be easily to mishear?

So you know how to refer to them to other people or in conversation. The order notes preference. So someone might use they/him, which means they prefer you use ‘they’ but if you use ‘him’ it’s okay.

Eh it's just arbitrary convention we landed on. You're right that it's redundant (as opposed to just "he" or "she", for example).

You will sometimes see people write something like "he/they", but that just means that either are acceptable.

It is redundant for the common pronouns. But once you step outside that space, people may need to see both. E.g., "they/them" is in the process of becoming established, so some will need the pair. And if somebody is using one of the neopronouns, most people are going to need to see both: https://en.wikipedia.org/wiki/Neopronoun

This redundancy is quite irritating to me. For most people, their pronoun is simply "he" or "she". Showing other parts of speech is only necessary for nonstandard pronounds.

Call me user, I'm going to use a fake name every time anyway. I couldn't be any less concerned with how I'm addressed by a machine as long as it isn't 'citizen', because I ain't picking up any cans.

Citizen! Pick up that can!

The issue here is that your proposed approach is very English-focused. Not every language would allow for a straightforward "pronouns" selector that would result in a meaningful data point.

Part of the discussion here is questioning whether the website is entitled to a meaningful data point.

I'm confused why it matters how you're referred to in the third person. I'm not trying to be snarky: but you're not there if you're being talked about in the third person (like a police report or a newspaper article), and if you're there, they will use the English "you" which is gender neutral.

I'm confused that you're confused. You're never referred to in the third person, either when present or absent? Or if you are, do you not care at all what pronoun they use for you?

Correct, it's never come up in my life, although I've heard 'ma am' awkwardly on the phone once or twice. It's hardly worth losing sleep over much less adding pronouns to user profiles. It's better off optional for those who want the message to be seen that it's important to them.

I find this hard to believe assuming we're talking about English here. Yesterday in a meeting somebody referred to me with a pronoun while speaking to the group. And I'm confident that other people use pronouns about me pretty regularly, in that I do that frequently about them.

If you're saying you personally don't care what gender you get referred to as, that's your right. But for other people getting misgendered can be a significant problem. If you want to change that, it's not those people you need to get to change. It's the ones making such a big deal about other people's gender.

First of all the world of online is different than the real world, where there's no parentheses or tags floating next to you. Meaning new people you've just met in a meeting, say, have no idea what the pronouns are.

If they're out of the norm then it may make sense to mention it then, I don't think society is hostile to it. I believe it applies to less than one percent of the US population, so it seems excessive to establish a norm of behavior for all, since harmony seems achievable despite that.

If there's a pronoun field then it might as well be free-form text.

For data collection purposes, a "sex" field is more informative than a "pronoun" field. That's not to say a "pronoun" field wouldn't be informative, only that pronouns supervene on sex except in outlier cases.

For what data collection purposes? You care more about whether I have a penis or vagina than whether I associate more with football and trucks or with dresses and makeup? If you want to know which ads to show me, the latter is going to be much more informative for you, even though gender is a weak signal for that. It's crazy to say that sex is more informative for all purposes. When I'm registering for some online service, why in the hell would you care whether I have a penis or a vagina?

I know that the differences between sexes is very relevant in a multitude of sciences. I'm not sure what gender identity is relevant to other than behavioral science and psychology, primarily applied to marketing. I would like to know more, though, so please share if you have any insight.

How much of that is because they forced it to be relevant? It's one of the few obvious ways to separate people into groups, so they did that for their studies. A popular categorization of humans before the mid 20th century was into three groups: "Caucasoid", "Mongoloid", and "Negroid". If that continued today, then there'd be tons of studies in the social sciences about how these three groups differ from one another, and it'd be therefore "very relevant" to a multitude of sciences. But we abandoned that false-trichotomy long enough ago that science does not miss it now that it's gone. It wasn't made relevant, so it's not.

Of course the arrangement of my internal organs is relevant to doctors and medical sciences. As is my blood type and my cholesterol level. That doesn't mean you should be asking for my blood type when I'm registering for an online service (unless, of course, that service involves blood donation or something). That's the whole point -- it's really, genuinely, just not relevant to the vast majority of cases where it's asked.

Oh, yeah, no disagreement with your assessment on whether or not a service should be asking in the first place. Just noting that biological sex is very relevant for something like disease susceptibility, along with a vast multitude of other things. It all comes down to those chromosomes.

Honestly, you could even skip pronouns. Just default to you & possibly they for third person references and write copy that avoids weird interactions of the word.

Difficult for internationalization.

That's exactly right. Asking for pronouns only really makes sense in a single-language situation, but most of the world's population uses more than one language.

On the one hand, you can't reasonably force people to select either masculine or feminine, particularly in English. On the other hand, if someone has answered the gender question with "neither / other" or "unknown / I prefer not to say", how would you refer to them in French, say? Would you ask "êtes-vous heureux", or "êtes-vous heureuse"? Unfortunately many languages do not currently have an established or convenient way of referring to non-binary people. (Though perhaps it's true that "most" languages are like Finnish or Hungarian in that gender does not feature in the grammar at all. The Indo-European and Semitic languages with which English speakers are most familiar are somewhat exceptional in that respect.)