Not agreeing with the comment you're referencing, but couldn't a comma work there? English is my first language, and thought you could use a comma or period there.
I'm far from an expert and I was only being pedantic because they were rude
That being said, I think it should have a period since it's two separate, complete thoughts. A semicolon might work, but I never figured out how to use those
That's fair. Their comment was rude and unwarranted. I'm no expert although I do write as a job (science though, doesn't really matter as long as you can understand what I write). But I do try to slip semicolons in wherever I can.