To be fair though KOs alone also arent the only way you pickup brain damage in fights, whilst Reem has been finished a lot he arguebly hasnt taken many really nasty beatings, the only somewhat prolonged beatdown that comes to mind for me is the first Shogun match.
By comparison I suspect something like Fedor/Nog 1 or the Cain/JDS rematches the loser probably took many times more long term damage.
Absolutely. That's why football coaches who are not Neanderthals are greatly reducing or eliminating hard contact in practice, and MMA gyms should be all about light contact sparring and drilling.
That's also why major amateur boxing events have gone AWAY from the headgear - the headgear and boxing glove combination meant fighters could pretty much take unlimited lower-level hits without being knocked out of their wits, which is potentially worse for the reasons you are mentioning.
Learning how to fall was HUGE and not easy to learn, IMO, for grappling and all-around sparring, for me. When one is falling, there's a big instinct to tense up that has to be overcome.
'Reem has been on the end of some tasty KOs, though. Those do damage, and make one more susceptible to getting concussed again. So while one or two, probably not a big deal, he's had a lot over his career. I'd be worried.
As these stars of the sport in it's popularity growth heyday hit their middle ages, we'll be hearing about more and more of them having issues, just like with American football.