My humble opinion as an ex-machinist is that nylon washers serve only one purpose and that is to protect the baseplate from scratches as also the
threaded pin of the top cap from possible impacts and vibrations during
shipping/transit .
Or -for example-when traveling with an assembled razor in the luggage .
Other than that the nylon washer serves no real purpose .
In fact ,when the razor is used along with a nylon washer few issues can occur .
The more threads are engaged at a bolt-nut joint ( as is the top cap threaded pin and the handle ) the force applied on the threads is more evenly
distributed -sort of speaking - .
Less threads engaged ,the higher the force applied ,mainly on the first couple of threads engaged.A typical nylon washer has a thickness of 1mm .
The most common threading used on most modern razors is the
ISO Metric M5 x 0.8 ,thus installing a nylon washer between the baseplate and handle effectively will decrease the
number of engaged threads by 1.25
( one full turn and 1/4 quarter of a turn or 450 degrees ) .That may seem a small difference but when one counts how many threads are actually engaged between the top cap and the handle with the baseplate in between ,
it becomes a considerable amount of
thread reduction .What all these actually mean ?
That a nylon washer does protect the underneath of the baseplate from scratches but has the opposite effect on threads.It can considerably accelerate thread wear.
The other issue is that nylon is not rigid.That "give in " transfers to the clamping of the blade.
It also may seem that is a negligible amount ,but considering that a modern razor is made with very low tolerances
( just think of blade gap and blade exposure numbers of 0.xx for example) ,it may negatively affect the clamping force applied to the blade.
Karve was supplying their razors with a small card that explained the reason of the nylon washer and noting that after shipping the nylon washer should not be used ,while shaving .
Chris is a machinist himself and he's aware of what issues can occur by
having a nylon washer on a razor ,
while the latter is being used .
Just my 2 cents .