@jkb
It's just social peer pressure to establish the rules by creating a discourse about acceptability...
Don't forget many people are living their first hands on experience of a federated network.
Rules are then a reassuring thing, knowing them and showing it, means belonging to the in-group in their minds.
@jansegers I think this happens in every social group, offline or online. Sometimes It's more blatant as is the case here because we explicitly discuss these matters, but every group has its own definition of politeness and good manners.