Here are some potential problems with sharing categories/topics across forums. I’ve been thinking of how matador permits people to follow other users across platorms. That actually wouldn’t be as fraught with some of the problems Joffrey outlined above for sharing topics between forums. But then there are concerns for following people, like:
https://meta.discourse.org/t/ability-to-follow-and-friend-other-users/1584/90?u=mcblu
Discourse has done a brilliant job of moving the culture towards the content (versus people) and it makes for a productive, professional environment. People do follow other people in a professional setting like linked in for example, but in that instance, you join linked in to network with professionals and find jobs. There are clear goals for joining linked in. You usually aren’t joining it to find buddies or develop insulated cliques that exclude other people.