Is it second person though? It feels like most of the times I've heard it in person, outside of a real livestream, it's sort of been for asking a question into the aether as emphasis.
"Chat, are you seeing this?" to emphasize something stupid they're seeing. It's not really spoken TO the person doing the stupid thing, it's spoken to this imaginary crowd to emphasize that what the other person is doing is obviously stupid.
I guess it sort of depends on who you imagine in the conversation. If it was actually directed at a real twitch stream chat, it would be second person. So not sure how to square that circle.
I've heard it referred to as a "fourth person pronoun" in that it also breaks the "fourth wall", and the excitement that English is the first language to invent a fourth person pronoun.
Though, I've also found Shakespearean scholars want to argue that while English did invent the fourth person pronoun, Shakespeare did it first with "Gentles" in several plays, most notably Puck's fourth wall break speech in Midsummer Night's Dream. (It is fun to give that speech with "Gentles" replaced as "Chat". To keep the rhythm you use the two syllable callout form of "Chat", which does exist in plenty of Twitch examples.)
I could imagine saying "God, are you seeing this?" to playfully emphasize something sinful they're seeing. Or similarly "Hey FBI, did you know about this?" to playfully point out that something is (or seems) illegal. Or someone says "Mike Tyson isn't that great a fighter" and someone else pretends to look at someone behind them and go "Hey Mike, what do you think about that?". It's all kinda just pretending some other entity is watching these events for humor, and I think it's all just 2nd person.
Or you could say something like "Chat likes it when I rap", but that's similar to "God likes it when I genuflect after making a touchdown" or something -- it's just standard 3rd person with a flair.
People have a tendency to over-emphasize how unique new speech patterns are. This same thing happened with "literally" being English's first "auto-antonym" -- it wasn't really, it was just a slightly different form of sarcasm. "OMG I literally died! Like I'm genuinely dead now. None of you are hearing this because I'm totes a corpse. I'm completely serious you guys, I literally have no pulse anymore." -- I can imagine all of that being in the same vein, but it's hard to argue that that means "genuinely" and "totes" and "completely" are all auto-antonyms too. Or that "riiiiiight" is an auto-antonym because it actually means "wrong". Things just aren't that new in language.
Ahhhh yeah I see what you mean. I'm probably thinking a bit too literally about 2nd person vs 3rd person. My example is an imaginary side conversation, where "you" = "Chat", so it's 2nd person, but the intent to me "feels" third person when spoken, as chat/God/Mike etc would never refer to someone in the room. (not that it matters in the context of labeling something 1st/2nd/3rd person in this case though) That's what's messing me up I think. Sorry about that.
And your God example, yeah maybe this is not a new linguistic phenomenon haha. I can very much imagine some middle age priests taking a jab at one another with "God, are you seeing this?" as father Percival takes another swig from the hip flask.
It is definitely second person plural. I have heard my daughter use it (deliberately ironically) many times not in the form of questions, like "Chat, today we're going to be making toast."
I admit that I have never heard it used in anyway except as a noun of direct address, so it may not be a full-featured second person plural pronoun.
Maybe like 3 years ago, people I know will use it exactly like y'all. Just last night I was hanging out with some (late 20's, early 30's) friends and my buddy said, "Chat, what are we having for dinner" exactly how you would say "Hey y'all...". This has become really common amongst young millennials I know.
I can't decide if I'm making a joke or not by saying that.