MY question is, where does this social pressure happen the most?
My hypothesis (no clue how to test this) is that the pressure is actually strongest between instances with similar interests and codes of conduct.
I'd expect a far right instance to have no influence on a far left instance, and that the default behavior is simply to block and move on.
I'd expect HIGH social pressure between similar instances, because there is an expectation to conform. "OMG, we hate Z, why don't you block Z?"