It seems to me that most of the Seinfeld plot lines come from something that we (the great unwashed) can relate to (looking for a parking spot, bad gifts/haircuts, horrible/wonderful girl/boyfriends, waiting in a restaurant, work frustration, etc). Where then does the check plot-line come from? It seems to be a clear metaphor for something - but what? It is simply a reference to all of us who suffer from CTS? Is it a comment on junk mail?
It doesn't seem to be a comment on checks in general b/c you can't write them in NYC.
It was too much a part of the show to be an aside.
This seems an impossible point to prove, or disprove, unless we can pry into the writers minds. But after watching the show again, I remain intrigued, if not convinced, by the theory.
12 centers, all of us!