I have a question about the pronouns in profiles. I hope it won't be perceived as transphobic, that's not my intention. I'm not a native English speaker, so perhaps that's where my misunderstanding (and possibly awkward turn of phrases) comes from.
Why specify the object pronoun when the subject pronoun is given?
For example, why display [she/her], and not just [she]?
Shouldn't the slash be reserved for people who recognize themselves in more than one gender, like [she/they]?
To the best of my knowledge, the convention is based on history. In previous decades, neo-pronouns like xe were proposed to serve as gender-neutral alternatives to he and she, and since they were new coinages, they didn't have commonly known objective and possessive forms, so all three forms where listed.
The pattern was so established that it carried over to he, she and they even though their declined forms are commonly known.
And now this is also just how we communicate that the speaker is stating their own pronouns. If I put "Pseu he" as my username, there's a high chance of confusion. If I put "Pseu he/him" as my username, it's obvious what I'm trying to say.
At least in the areas where I see pronouns, they often do it in their status or the like and may not use brackets. "He/him" seems to be more widely understood than brackets or parentheses.