Currently, the user can filter the topics displayed, by selecting another status or another tag in "Status: All" and "Tags: All".
This could be made more powerful:
1) by adding a checkbox symbol on item selected in the selection menus:
=> for instance you could select several tags simultaneously:
to filter topics with "Features" and topics with "Urgent!" (a OR in fact ;-))
Of course, if you click again a selected item in the menu, it would remove the checkbox symbol (2-states)
2) by adding a 3-states symbol on menu items (instead of 2-states suggestion above)
=> by clicking a menu item, then you would get: checkbox symbol, forbidden symbol, no symbol (and so on in a circular way)
The new intermediate state "forbidden" would enable to ignore the selected item in the displayed topics.
All that filters combined would give:
DISPLAY any topics satisfying "any of the checked items" and NOT satisfying "any of the forbidden items".