Wow. That blog is pretty intense. Well at least they gave them very concrete advice about how to approach the waitlist process. I have been left in limbo wondering if I should be trying to send new materials, references, stay in touch with admissions, etc. But my SO actually dealt with the WL process too and ended up being accepted, so I know it's possible, although he was in a very different program (PhD in the sciences at MIT - hence why I did not just forget about HKS and enroll at Georgetown or SAIS).
As for HKS, I am keeping my fingers crossed for an update next Monday, since that will be one week after their extended deadline, and the last promised update was to be one week after the original deadline.