What would be a good reason, if any, for someone to take out a thermostat so that the coolant is constantly flowing in a older RX7 and sells it without mentioning?

 

I couldn't tell you why someone would do that, other than the possibility that they didn't know what they were doing and thought they were helping something. What i can tell you though, is that the removal of the thermostat will cause the ecu to go into limp mode and gas mileage and performance will suffer.

 

There wouldn't be a "good" reason.
Stupid and nefarious maybe, but not good.

 

Honestly there is no good reason, the only thing I can think of is that they have the same misconception around that idiots around here have that it makes it run cooler, which is not the case. Now I have before in my race vehicles decored it to make a restricter and ran that.

 

As it's been said, the PO probably thought they were helping an overheating problem. Problem is, without the thermostat, some of the coolant is always bypassing the radiator (as the thermostat opens, the bottom of it closes the bypass passage).