Nyadach, as a T2 not on insulin I don't have anything to contribute to the OP's question, I have however been on a 30 to 50 g/day diet for 4.5 + years. I am curious what type of mental damage I may be facing?
I work in IT and make my living with my brain, believe me I would notice a decline in mental function. So far I seem to be holding my own. Here are a couple of articles, article 1 and article2 which together say that our brains are quite happy switching fuel from glucose to ketones and that this ability is probably a vital evolutionary adaptation. Both imply that ketones are a more efficient source of energy and also burn cleaner producing fewer harmful byproducts. They also make the point that the long term effects of a ketogenic diet have not been studied.
I would also dispute the claim that
Bernstein's system seems fine if you sit on a sun lounger all day
Here is an article about an experiment of N=1 conducted by Peter Attia MD and endurance athlete. His conclusion after examining the results is
The one drawback, it seems, to completely eliminating carbohydrates from my diet was a loss of all-out top end power. For someone like me, this doesn’t seem to hinder performance too much, but if I was trying to win an Olympic gold medal in the 400 meter run or the 100 meter freestyle, it seems I’d be better off with some carbohydrate in my diet.
So what did I learn? Keto-adaptation made me far more metabolically flexible and efficient in the aerobic environment. This seems particularly important for folks who compete in events longer than a few minutes (e.g., 10K, marathon, triathlon), but less so for folks doing short-burst activity
To be fair Attia switched to a ketogenic diet when he saw unmistakable signs of metabolic syndrome in his own body. Cutting carbs drastically successfully addressed this problem. Since he is neither a T1 nor an insulin user, his experience may not be relevant to either you or the OP.
Characterizing Bernstein as a quack implies that all the folks around here who have derived benefit from reading his book, even if they don't strictly adhere to the 30 g/day, are either lying, delusional or brainwashed in some way. I think this is completely unfair. We each have to find our own way but attacking those who are following a different path is not useful. If you have found something that enables you to meet your blood sugar goals great, tell us about it, but always remember others may have found a different equally valid path.