Let's make it a little more topical: Both people were told not to play with the gun and that there were insufficient ICU beds. The first person still played with the gun and shot himself and another person. This was a personal choice he made. His luck was against him (and the person he shot).

Let's make it more topical still: The two people were told, "Look, we know you want to play with guns. We really don't want you to. Receiving treatment for gunshot wounds is less likely to lead to long life than simply not getting shot, and we have other illnesses we need to treat. Here's an additional incentive: if we don't have sufficient medical resources to treat everyone, the people who ignore this warning will get treated after those who don't." Yes, this is coercion, inasmuch as it is influencing their decision, but under this definition of coercion, coercion hardly seems like something to worry about, certainly not as much as getting shot.

Should vaccine refusal then result in increased premiums, or increased coinsurance for covid-related care? How many people would make the choice if they had to bear even part of the expected value of their increased medical costs themselves?

Although I don't know of any insurance companies that have rates for people that have not undergone certain medical procedures. That sounds unethical to me.