IMO the only real problem with using the shins (prior to conditioning) would be striking hard targets. If you strike your opponent in a "soft target" area, it wouldn't matter as much. The thighs, backside, the gut and even up into the torso probably wouldn't hurt your shins at all.
If you hit bone with your shin, that's when the pain starts. Especially shin to shin...
What are the preferred targets used in Muy Thai? As you can tell, I have had very little exposure to Muy Thai.
When we use a knee strike, we are using the muscle on the inside of the knee, (the lower quadricep) and stay far away from the knee cap as a striking weapon. This is a very quick, close range strike that can be used repeatedly, very similar to the shins (I presume). Is that the primary reason Muy Thai uses the shins?
THX
SZ