We've got Discourse running with private categories. When a user without access to the private categories type a new topic, they are presented with topics in categories to which they don't have access.
I see, so the dyamic duplicate topic suggestions when you are composing a topic leak the secure topics. Sorry about that, will fix -- @eviltrout can you have a look?
Yes, you stated the problem more clearly than I did. Thanks for the attention!
Fixed a while ago, sorry about that!