Is Descending Armor Class the "sacred cow" of the OSR?
Is it the one thing some folks have decided to draw the line at?
I can actually understand the desire to remain "true to the original form" and I personally found the change of the later editions of D&D to Ascending AC as an affront of my personal ideal of what defined D&D.
I started with AD&D 1e. I didn't get a DM's shield for years (and initially refused to cut up my issue of The Dragon to remove and set up the Combat Wheel). The pages of the Combat Charts in my original DMG took a hell of a beating over years of use, all because of the constant need to refer to the Combat Charts.
The thing is, as I've gotten older, I care less about "the purity of the game", which I suspect is where the line between Descending AC and Ascending AC gets drawn. Ascending or descending, the results are the same but with ascending AC the math is simpler, as there is next to no math. You roll to hit AC. Add your modifiers and you are done. You know if you hit right then and there.
With descending AC, you either refer to the chart OR add your target's AC to your modifiers roll to hit and if the total is 20 or higher you hit. I think that's how you go chartless with descending AC. This would be THAC0, kinda sorta. THAC0 was an attempt to move descending AC away from the combat charts. THAC0 gave you a starting point with some of the math filed off. It certainly helped.
Player's have it simpler in either case, as they can writet down their standard To Hit array on the bottom of their character sheet.
DMs don't have that option.
I'm NOT going to re-gigger my 1e / OSRIC campaign to use ascending AC. In such an attempt lies madness. I am going to spend an hour or two writing the THAC0 for all the creatures in Rappan Athuk's immediate levels, so I can save some damn chart referencing time during game sessions.
I still think ascending AC makes more sense, even if descending AC is more authentic.