It might be fun/interesting to try to base the latency upon simulated geography: whether the entirely fictional geometry of something like classic GeoCities where you get assigned a random address in a digital "neighborhood" somewhere when you sign up, or use real world geography and filter it through ancient routing restrictions like "how long would it take in the post by horse/carriage".

A benefit to a dynamic latency such as simulated geography would be that it would make it even tougher to sync together how posts would be arriving from multiple users (unless you were targeting a specific user).