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You are wrong on both counts.

I just addressed "you", even though you're not physically present, so clearly that's not a requirement of second person usage, not to mention that presumably this child saying "chat" is being heard by people physically nearby in this example.

In order to break the fourth wall, the speaker must be part of the media. In the instance of streamers talking to their fans, it's clearly meant to be an interactive experience between streamer and host, consuming the same media (albeit in different ways). They're asking a question and getting a response which informs their actions.

Fundamentally, it's no different than when my wife asks "did that wizard just cast fireball?" while she sits on the couch watching me playing Skyrim.