At my office we have this culture where there's no such things like 'a wall between manager and staff' or 'strict, polite formalities between co-workers', but it doesn't mean there's no respect here.
One of my bosses sent me an email regarding my finished task and cc'ed an other manager and director (all higher-ups in my office). After a while things started getting funny and seemed to get 'out of bounds', because the bosses started to joke around. I (as a staff member) don't have any idea how to interact with them.
Should I join the email conversation or simply watch how things go and reply only when prompted to?