From Fallen London Wiki

Action purge is not allowed on comment pages.

I'm fairly certain the problem is specifically that <a href="/wiki/Reveal_a_regal_truth_to_the_Glasswhisper" title="Reveal a regal truth to the Glasswhisper">Reveal a regal truth to the Glasswhisper</a> has not had its result added yet. You'll notice that page is not currently in Category:Retired. (Not sure where that idea came from.)