Personally, I see this along the lines of: "Are you the sort of loser who would thank someone for sex?" The noder/chinger relationship is symbiotic: he who pens a ching-worthy write-up gets the "brownie point factor" of a pat on the back and a job well done in the form of a tiny "C!", and the chinger's life was enriched by either a filled gap of knowledge or a nugget of nostalgia or whatever caused them to ching the writeup and disengage the Cool Safety.

Unless, of course, you paid for the ching, then I guess it's perfectly all right to thank the person who gave it to you.

As a side note, I'm exactly the sort of loser who thanks people for sex, so I constantly send messages of appreciation to Those Who Ching Me. Well, except for P_I, because the only response I get out of him is a snide message saying "Please stop thanking me for cooling your writeup."