Which one do you guys identify under?

Most Hexbears support a state that works for the interests of the people, referred to as a Dictatorship of the Proletariat that would be established after a revolution, as described by Marx. Then there are some anarchists who also support a revolution but not a Dictatorship of the Proletariat. The rest ideologies are far too minimal to notice

so I initially thought the instance was more of a shitposting community rather than a serious one advocating communism

It's a shitposting community. Probably the most well read and informed shitposting community you've ever come across though I bet (not that that bar is particularly high). lemmygrad.ml is the serious and educational instance though only for Marxism Leninism and no other ideology

but is the shitposting and trolling done on purpose to antagonize other instances

Many people have stated they only shitpost and troll response to people who are bigoted, or commenting in bad faith and not looking to have an honest discussion or learn, unlike you