In the editor typing @ or # offers completion to link to users and categories, respectively.
Stackexchange offers a [tag:tag-name] tag to link to messages of a tag. I cannot seem to find such functionality here. Am I missing something?
If I’m not missing something, here’s how I’d use it. I’m using Discourse to run online classes and have people add tags to their solutions to the assignments/challenges I give them. It would be handy to have an easy way to create a link to all of the topics with a given tag. (And it would save, maybe a dozen keystrokes each time I add such a link! ).