What is the term for strangulation where they don’t leave a mark and the larnyx isn’t crushed? He knows.
I don't recall seeing such a term, fv. Strange to say, most strangulations leave either no external marks, or marks so faint that even ERs commonly miss them. When the trolls gloat that no external marks were found, they aren't really making a point -- that's the NORMAL status in strangulation.
You may be recalling the chokehold that Michael and his brothers used in roughhousing. (As I recall, Michael did it to Bobby once, too.) It has a lot of names such as blood choke or carotid sleeper hold or shime waza in judo. It works by cutting off oxygen to the brain by compressing the carotid artery. This can cause unconsciousness in TEN SECONDS! With enough force, the hold can also crush air passages (= choking). Either way the victim will quickly pass out for lack of oxygen.