I think you've found a wider oversight here.

What do you mean specifically Chris?

Ok, I was mistaken. I thought blocks weren't considering validation privilege and caching separately. But they cache separately by group which achieves this.

However, this issue 2 separate issues:

1) A bug, topic validation should be considered by the blocks. Fixed now.

2) Behaviour that the core design of the activity feed doesn't include (the activity is the submission of the content, so it is just listed verbatim) - it's not an activity-after-moderation system. This is the case for any content type, not just topics. I'll create a separate issue for this - I do think it would be best corrected, but it's not at all trivial because activities are log entries and therefore we'd need to do some juggling to write those out only when validation has happened, or make them check validated status when displaying, or copy and maintain a validation flag into that table.