Thank you for creating this topic. I am slightly annoyed by this warning, too. I don’t see a warning for using bug in my reply, so this seems to be limited to category mentions. I don’t remember when this started, but I just tried, and it doesn’t happen on a forum that is still on v3.6.0.beta1-dev.
I am not sure I agree with that. I usually find it quite helpful when I am told that a theme component has already been linked in a topic. Sometimes I miss that something had already been suggested.