The Brief: Including one's preferred pronouns, such as She-Her-Hers or They-Them-Theirs, in their social media bios is a step towards normalizing the practice of sharing pronouns and creating a safe-space for non-binary identifying individuals.

DEEP DIVE
As with just about anything, while you may not understand it, it’s important to respect it.
In recent years, sharing one’s pronouns in their Twitter and Instagram bios has become somewhat standard, especially amongst the LGBTQ+ community. Gender neutral pronouns, such as They-Them-Their and Xe-Xir-Xem, are often used by members of the LGBTQ+ community who find standard binary-specific pronouns unsatisfactory for identifying themselves.
People who support trans rights are also making their pronouns known. By doing so, they can normalize the practice of sharing and more importantly, respecting preferred pronouns. As a result, people who use non-standard pronouns to refer to themselves are treated the same as everyone else.
Preferred pronouns often refer to sexuality or gender. Therefore, it’s important to avoid making assumptions about someone’s pronouns based on their sex. By asking for everyone’s preferred pronouns, regardless of appearance, it will become easier and more comfortable to move through the world as a trans person.
Side note: if you don't have your pronouns in your bio, please consider it. It doesn't hurt anything and it's an easy boost to your trans/non binary neighbors. Nothing lost, only support gained.
— Amanda (@juuust_amanda) July 23, 2019
this is your regular reminder that misgendering a nonbinary person is just as bad as misgendering a binary trans person. additionally, not every nonbinary person uses they/them pronouns and using they for a person you know doesn’t use that pronoun is misgendering.
— Sascha 🐦 (@confusedophan) July 23, 2019