For whatever it's worth, I've run my MacBook Pros in "clamshell" mode (e.g., lid closed, connected to an external monitor and keyboard) all the time -- I did it

For whatever it's worth, I've run my MacBook Pros in "clamshell" mode (e.g., lid closed, connected to an external monitor and keyboard) all the time -- I did it with every work Mac laptop I've had and with my personal one back when I was using it as a desktop. I know there's lots of "never do this with a MacBook it will overheat!" advice out there, but it was just never an issue for me, and this was across enough different devices and generations that I don't think I was just consistently lucky. Are you describing something else, e.g., closing the laptop lid without connecting an external display and preventing it from going to sleep? I never had an issue with that when I was using Windows work laptops, either, except that I recall both ThinkBooks that I had seemed to have about a 50% chance of a full kernel panic style crash when I unplugged the external display. This was back when ThinkBook was an IBM brand, though, and IIRC I was running Windows XP on both.