This hint isn't just controversial; it's flat out wrong. As others above have pointed out, it's not possible to reclaim memory from leaky applications in any way other than quitting them. And purge-ing is of questionable utility anyway.

I would recommend that kirkmc delete the hint entirely so that it doesn't mislead people with incorrect information.

While I see that it may be mis-titled, it seems from some of the comments, and my own experience, that there is some benefit to the purge command in certain situations. I also linked to an alternative to purge that may do a different type of memory reclamation. If the post were reedited to reflect the contents of subsequent comments I think this would make an informative and useful hint.