http://feedback.wikidot.com/system:page-tags/edit/true - I was given edit rights a while back to this part of the site. The ListPages code is:

[[module ListPages tags="@URL|non-existent-tag" category="wish" perPage="50" separate="no" appendLine="[!----]" order="rating desc"]]
||~ Rating||~ Title||~ Creator||~ Tags||~ Status||[!----]
|| %%rating%% || %%title_linked%% || %%created_by%% || %%tags%% || %%_tags%% ||[!--
[[/module]]

When I copy the same module over to my own site (just changing the category) it works properly. So there seems to be something wrong on the Feedback site itself.

All the wish pages have normal tags for the subject and hidden tags for the status. I know they have normal tags as well because I added most of them! So it should be displaying these pages in the ListPages module. The tag cloud and listpages worked fine up until just a few days ago. Something has changed but I'm not sure what.

Even though the default is pagetype="normal", if yu specifically add this the ListPages module doesn't display anything. So something wrong is happening in the background.

I suspect someone has added the non-existent-tag part of "tags="@URL|non-existent-tag" but I don't know why and it seems to be that which is causing the problem.

Edit: Ahh the non-existent-tag just makes sure that the listpages module doesn't initially display anything

Seems you figured it out :) Came here to reply to your question.

As 'non-existent-tag' isn't on any pages (at least, it shouldn't be), no results are displayed by default. As soon as something is provided via URL, it should override that value.