More inferences
I hesitate to send more without permission from the author Wong.
But, as you know, there are other ways to estimate what the other
players' cards are. One way is to ask the other players to show their cards. Sometimes a congenial table will show one another their cards before taking insurance.
Recently, I was playing beside a gentleman who stated that he always insured 10-10, so when he insured later, I subtracted two off the count. Later, he insured and said "the dealer has had blackjack every time and I'm insuring", so I counted that as 0.
Your mileage can vary. For example, recently, the other 3 players tucked. Less than one deck remained to be dealt, with my max bet out. I inferred a true count of +1 and did not insure. But they had 9-6, 9-6, 8-8, totaling a +2 instead of the -3 that I inferred! I had seen they were not strong players, but that was a shock.