Requested feature overview description.
A Content-Deleted check-box (similar to the Active box) within "Edit" on a pool's page.
The checking of this Content-Deleted box would add a symbol (perhaps an X?) in front of the pool name.

Why would it be useful?
For understandable reasons, pools can only be deleted by admins and (according to a thread I found inquiring about how to flag pools for deletion) admins often prefer to keep pools around in case they end up up-deleting the content at a later date. Some way of flagging pools currently full of deleted posts would make paging through for interesting stuff to read easier, as we wouldn't have to click to see that a pool contains nothing viewable. If content is ever un-deleted the admin could, at that time, simply uncheck the Deleted-Content box.

What part(s) of the site page(s) are affected?
The Pool listing page.

As a lower-effort approximation, could we put some easily-searchable keyword in the pool title? Maybe "[Deleted]" or "[DNP'd]" or something like that.

Maxpizzle said:
As a lower-effort approximation, could we put some easily-searchable keyword in the pool title? Maybe "[Deleted]" or "[DNP'd]" or something like that.

I had considered that, but pool names can't be changed after the first week except by the pool creator