I don't read it as informal. Childish or lazy perhaps, at best. When you intend it as "inviting informality", you're implicitly doing this because "formality"

I don't read it as informal. Childish or lazy perhaps, at best. When you intend it as "inviting informality", you're implicitly doing this because "formality" is too much effort. The thing is you're not inviting, but rather demanding. You have decided the conversation is informal and low effort, and that's how you'll treat it, without considering the person you're communicating with. This is of course all a lot of strong statements and these things don't matter as much as this sounds. I don't feel _that_ strongly about these things, but the lowercase thing always strikes me as just plain weird, and deconstructing why I feel that way this is where I get to.