I thought I had come across an article on this on Getting Stronger, but I'm having difficulty finding it at present. The main thing I'm seeing now is this comment:
The key here is adaptation: It’s dangerous and silly to expose yourself to water or air temperatures beyond your adaptive range.
There are probably two different things going on here.
One is staying cold for a fairly long time (many minutes, hours?) at the around-shivering levels, which your link seems to be talking about. The main effects would involve hormonal adaptation, brown fat, etc.
Two is a cold shock -- very cold, but very briefly (seconds, maybe a minute or two) -- the response to which is likely quite different, mostly vascular and with a different set of hormones.
Also, I expect the "adaptive range" of humans with respect to environmental temperatures to be pretty huge :-)
To the fun theory, hedonic treadmill sequences.
http://gettingstronger.org/hormesis/
TL;DR stoicism with science.
Key idea: OPT, Opponent Process Theory: http://gettingstronger.org/2010/05/opponent-process-theory/
Research, PDF: http://gettingstronger.org/wp-content/uploads/2010/04/Solomon-Opponent-Process-1980.pdf
From the article:
"In hedonic reversal, a stimulus that initially causes a pleasant or unpleasant response does not just dissipate or fade away, as Irvine describes, but rather the initial feeling leads to an opposite secondary emotion or sensation. Remarkably, the secondary reaction is often deeper or longer lasting than the initial reaction. And what is more, when the stimulus is repeated many times, the initial response becomes weaker and the secondary response becomes stronger and lasts longer."