This is a 2-in-1 question, I suppose. I type the way I do. I’ve always typed this way, but I’ve noticed when interacting with people (not on here) that people always think I’m far older than 19. They think I’m in my forties or fifties.
Also, I tend to type using full stops, which people may think are rude. When I’m typing a full sentence, though, I end it with a period. If I say, “He’s being an asshole,” (with a period), I mean that as a fact, not out of anger. It just happens to be ended with a period since it’s a sentence.
Older people grew up writing less than younger people have, because of texting, so they’re more accustomed to taking their time with the proprieties of grammar. Younger people began using grammar as a tone marker differently from how it had previously been used, so they tend to see a bigger difference between “no” and “No.” as an answer to a question than older people do. For younger people, the latter tends to seem more abrupt and final, which could come across rudely.