“Friends, Romans, countrymen; is this true?” or “Ladies and gentlemen, The Weeknd.”

if you used “y’all” to refer to the groups in these examples, “y’all” is a pronoun.

Addressing someone does not require them to be present or real, so the presence or absence of a literal chat does not somehow transmogrify this noun into a pronoun.

Chat is a metonym (not a pronoun) when you are referring to a group of people in a chatroom, real or imagined. That’s part of the new usage. What’s also part of the new usage is using “chat” but you aren’t thinking about the people you are addressing as part of a chatroom.

Plus we gotta examine the underlying context of how this usage started and how it has evolved. So it starts not as a pronoun when streamers start using it. Then it mutates as people start saying it in real life, outside of a streaming or chatroom context. So let’s say a young child hears someone say “chat, is this true”, and, without looking up what this means or the context, just starts saying it, without knowing what a chatroom is or without a specific audience in mind. I think at that point it becomes a pronoun.

Anyway, none of this is anything to get heated about.