They (singular) has been used since at least Shakespeare, so every single student in an English-speaking country has learned how to use it correctly; including how to format sentences using singular they. ‘The firefighter rescued a puppy from a burning building; they were really lucky they spotted the puppy in time.’
In any sentence where two pronouns are the same, you’d replace one or the other (preferably the latter though the ‘rules’ on this are stupidly complex). Alex was drinking Jim’s coffee. He should really buy himJim a replacement.
This is a serious problem I think isn’t actually talked about enough. There is a ‘ring of trust’ on most social media now that in my opinion goes far too far; if you don’t have enough algorithmically determined ‘trust,’ you’ll be booted off without a way to appeal. Reddit shadowbans the vast majority of new accounts, but hasn’t been able to cut down on spambots; Facebook by its nature needs ridiculous amounts of personal information but even then doesn’t actually use it to assign more trust since bot-owners can supply generated information that’s equally as valid; really all social media, especially if you do anything at all to protect your privacy, assumes you’re a spambot first, then only lets you participate after you prove beyond a shadow of a doubt you might be a human. I understand we’re already half way into developing a dead internet, but there’s no reason we need to go full throttle into it by limiting actual humans from signing up past a certain point in a product’s lifespan.