Hi, Alfred,
There’s some information available here about the various Trust Levels that Discourse uses. I know that I can pin and unpin topics for myself, but not for others. It appears that “permanently” pinning a topic for yourself and others is a Trust Level 4 (Leader) privilege. There’s a discussionhere about some of the issues with not having the ability to create unit-specific Discourse “Leaders”, so, if I understood correctly, anyone who is promoted to Trust Level 4 effectively becomes an admin for all of the forums.
