Mutliple user blogs

Sounds like the Authors system that WordPress has in place (I could be mistaken). Either than or the other sites you refer to might be using a blogging platform other than WordPress.

Projectego is right. Maybe another platform. Or a hacked WP. By default, WP authors links have the word “author” in them…. like domain.com/author/username. Someone might have done some hacking to make it read differently….or maybe they have each category named with the name of a user, and each person only blogs under their own assigned category. That would create URLs sorta like what you described.