One way to implement a hotlist is to label the actions on the hotlist with "A" and leave everything else labelled as "B". These can be called "AB priority codes". (Some people use stars, flags etc.) David Allen says "The "ABC" priority codes don't work." It's not clear to me whether he means all systems of marking priorities with A, B and C. or some particular system that involves doing that and using them in a particular way. It seems to me that he means they don't work for anyone, though mcogilvie says "When David Allen says it doesn't work, he means it doesn't work for everybody, all the time."
In any case, apparently there are a number of people (including, perhaps, David Allen) who find that AB priority codes or equivalent work for them, but not ABC priority codes. That's fine; but there are other people (including myself) who find that a larger number of gradations in recorded priorities of next actions is more effective for us.
To bcmyers2112: Thanks for saying "Your mileage may vary." and "I think what we have here is a failure to communicate." I appreciate it. Yes, I think we're having trouble communicating. We can try to work through that and figure out what's going on; or we can drop it. It hasn't been my intention to criticize anyone, but to discuss ideas, opinions and reasons. I'm sorry if saying "straw man" very briefly came across as impolite; I'm not sure what's the best way to express that idea.
Inability is an abstract thing involving comparison with alternate universes; it cannot be experienced.