I hear it often - I have submitted papers to journals and they required single space after period. Mostly work related stuff, where I'm like... seriously just clean it with a formatter.
Plus if you do any type of actual engineering or technical writing, you probably come across it.
I've seen posts about it on LinkedIn; on sites related to web design (and browsers don't even care, they let you type with the extra space but don't render it anyway - I KNOW I put in two spaces in this post and in preview it eats them, best of both worlds), and the above mentioned journal.
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Regarding insurance - interesting, I've never had anything of mine get denied. Closest I've come is my son got hurt at school on the playground because he was goofing off, and the insurance company keeps sending me questionnaires related to subrogation. I don't see why the school's insurance would need to pay for him falling when he was hanging upside down (it wasn't broken playground equipment or anything). Also it's not like they are going to refund the $1000s I had to spend out of pocket even if it they get the school to pay for it.
I still maintain that a primary reason health care is expensive is because of insurance - public or private. The reason is if you can use "money from all the people" to pay for care for "some of the people", then of course the prices are going to rise. It also doesn't help that insurance is tied not to statistically rare events but what is effectively a statistical certainty; "insurance" doesn't work well in those situations.
Maybe we need to ask AI how to have a system that minimizes individual financial risk of a health event without resulting in massive regulatory capture and monopoly power in the health care industry. I've thought about it from an engineering perspective and haven't been able to come up with anything - probably because it involves people and social structures rather than laws of physics.