There's no real style guide.
Looking at the comments, there's a few things
- The presumption of the gender of an unknown subject. The default pronoun folks get taught varies wildly. In my time/culture it was "she/her". Some folks default to male. More recently - the singular they gets used more. I have an easier time with it since it's a common form in my native language, and the default in the specific dialect I prefer.
Practically since most SE sites frown on salutations and noise - quite often you'll find that talking about a topic, you will not hit these things as much.
- Practically, some folks may prefer specific pronouns. For example, some folks are non binary, and may prefer They (or other neopronouns). There's no standard style guide for this and frankly I'm out of touch enough in academia not to know if they are updated to this. I don't even remember that being mentioned in said style guides, which seemed focused on very non personal, serious writing.
While it's a little after when I needed these things, it seems modern revisions of style guides do cover some of it, including the Chicago Manual of Style do include the singular they. I find that they're more useful for business and formal writing over SE answers. It's fine to use one if you need it, but worth being flexible if you encounter things you have not before.
In many cases though, you can get away with social cues. Typically if it's clear someone prefers a specific pronoun then it's a great idea to use it.
- You may find that in the non social environment of Stack Exchange, that you might actually come across this less than you expect, and in the first case, at worst someone would enquire.
You'd never have to go "Hey Guys!" here, to borrow an example given. In many cases you dive right into processes and details over people. On SO for example, folks are more interested in your code. Most of my SU answers generally don't involve humans.
as an aside, as far as I can tell I've used no 3rd person pronouns except when talking about them in the above post