Great question! Martti would be best to answer this. Having spam filtering system without impacting user adoption is extremely crucial.

Iris is based on active user engagement so is you are an existing user, it’s based on follows and engagements (likes, comments etc). if you are a new user, you’d probably be engaging in circles you are keen on. So far my followers count only differs by 2-3% if I compare it with snort which is low delta, and the reduction is likely due to passive users.

Additionally Iris’s social network is based on configurable filter so if your N=3 friends of friends is too tight a circle, you can expand the degree of network.