Who decided to create a Hexbear dialect here as a mainstay and why? (Things like bazinga)

bazinga comes from the "young sheldon" tv show. it's used here to refer to liberal technocrats who believe the problems of the world can be solved with sufficiently advanced algorithms, that humans are simply waiting for someone smart enough to come along to invent solutions to the problem caused by capitalism.

the treat discourse is a slowly simmering struggle session about how leftists in the imperial core should interact with the treat economy, whereby behavior is incentivized by access to treats: minor luxuries, tasty but not very nutritious food and snacks, the carrot of capitalism's carrot and stick. "slop" is hog feed and we're the hogs, demanding content, entertainment, and treats.

"adults in the room making/doing hard decisions" is just making fun of neoliberals and centrists who see themselves as mature, responsible, logical, rational, capable of setting aside their emotional reactions to atrocities around the world in order to wisely compromise with the people committing those atrocities and benefit materially from them.

there are a few users who use these terms more, but i don't think any one person was responsible for coining them.