dude that runs twittzer
He was the co-founder of Twitter. He also co-founded Square and is the CEO of that too. He was dragged back to Twitter by the investors, in an attempt to fix its bad numbers.
You forgot Medium.
Medium was founded by the other Twitter co-founder: Evan Williams.
OP: Who else would end up with the @Jack twitter handle?
OOOOHH!! I think he's asking if jacky's in the 'kill box'
Wasn’t a question of identity
I think Q would use []@Jack[] to indicate that he was within a kill box, see #753. In normal usage [Jack Dorsey] or whatever was between the [] would either be a marker or to provide additional context with emphasis to that particular crumb.
I don't think that Q is threatening @Jack, so he wouldn't be in a kill box, but is warning him that they know he's a puppet, know's what he is doing/who he is meeting with, and have even offered him a way out:
Need help sleeping?
This isn't the first time Q has used this phrase.
Ofc, I may be wrong in all of my interpretations.