It's actually the complete opposite. It makes things so you don't have to choose a single topic to post - you can select multiple topics to post in (since the PVB only has one though, there will be little change here in that regard). Same with deleting - if it's removed from a topic, that doesn't necessarily completely delete the post until it's removed from all topics.

The banning from individual topics works exactly like banning from a message board now - I just added that to emphasize that global posting won't affect the ability to ban from individual message boards.

I think the confusion came from the terminology. Basically, topic = message board. It just has a different name.