As someone who both reads and writes a LOT of emails/messages as part of their job, I go by two simple rules:

Let the situation determine the level of precision in your writing/grammar.

Always reread what you have typed at least once. Sometimes more depending on the situation.

You take the time to write it so that someone else will read it, and then understand it. If you read what you write and feel it’s concise, it’s good enough. After that is someone wants to be a pedant about it, they can suck shits.

It can be pretty clear (especially on the internet) when someone hasn’t read what they wrote.

To me, that’s the line between an acceptable post and a shit one.

That, and whether or not you completely agree with everything I have ever thought, ever.