I wonder could you tell us where you read that, or which aircraft you experienced it in Lomcovak? I've had carb ice in a variety of circumstances, including an O360 that was actually below 1000rpm due carb ice with throttle closed, and carb heat fixed the problem within seconds. I think it's quite important that pilots have confidence that carb heat will fix carb ice if applied promptly.
Well Lomcovak is correct there. Do not rely on carb heat to clear ice if the engine has been operating at reduced power settings for any significant amount of time! I've had carb ice build during low power cruise and carb heat really struggled to clear it. That was with a C90 which is very prone to icing, but it does prove his/her point!
Bookworm,
As I said in my answer to Lomcovack, I think it is very unlikely detonation would occur and I believe you are correct to think leaving carb heat "hot" is (whilst not suggesting it's the right thing to do) moving away from detonation regime as you say. He/she? is right though, that if the engine is over heating, then hot air could induce detonation. However, in the context of this subject I think it's a bit far fetched to expect detonation by leaving hot air on by mistake, unless the subsequent climb is very steep, under full power and under extreme conditions!
SS