The inspiration for this page is reading the first edition manuals and seeing it very clearly spelled out that hit points are not purely a measure of health, but instead of health plus luck, focus, general vigor, etc. In fact it claims that the HP at higher levels would be absurd if they were meant to mean actual ability to take damage. This struck me becuase I've seen various proposals for making HP measure something other than health, and this is always presented as something "far from how HP are used in Dungeons and Dragons," but in fact they were that way from almost the beginning. (The original rules are vague, as they are on most things, saying only that HP measures "the points of damage that can be taken before death" but it's not made clear what exactly "damage" consists of from a flavor sense.) It's not until 2nd edition that you start to see language reflecting the idea that they measure health only.
I am sure that there are many other subtle differences between the editions like this, and the point of this page is to catalogue them as I see them (and when I remember.)