1) About pairs, they usually can easily classify them post flop. You regularly can deduce someone got a pocket pair (especially if there was some fight preflop, per example if an ace come and they take a medium chip).
And two pockets pairs can easily classify them if another player got a pair between those two pocket pairs.
And they are far rarer in probabilities. The top 16.67% of hands will make A5 being between 6 and 5. So by giving a whole chip for pair, you make all non pair hand much harder to classify, and I'm convinced it's not worth it.
Though, about putting pairs in all chip, I have no opinion, just most players put them at 6, so I follow them, it seem both options have upsides and downsides.
About coordination that's why 'high card promesse' is mostly only talked about in higher table, where people debrief after game, and look at every clue they can get about everyone.
But so having a more probability based table (like making A4/A3/A2/JT being in a weird position, is more versatile (atm in the wiki page, I didn't ranked those four hands).
2) After asking someone which play with 'high card promesse', they tell me that it's worst at 5p. Mostly because Queens are in a weird position, and need to be added one way or another: pairs A / K / Q J / T 9 8 / 7. You end up with chip with kings having really few hands.
3) I fully agree with you, you explained my position very well. One counter argument is that the more you play with the same player/the same community, the better the players become. And so any good players which got something out of place should slowly change, and any habbits should become more and more known.
But personnally I like to said that I try to put myself at the right position while giving the lowest amout of information possible about my hand. In 98% of cases that change nothing and I still play 'normally', by trying to know my exact position, but in some cases (mostly when I pick last), per example if I'm between 4&5, and everyone else picked 12346, then I would not pick 4 then 5, I would pick 5 directly. And so others would not know if my hand is a very high 4, or if I was late and I'm just 5.
And personnally I talked about it in another subject, but I like putting the hands like Q2/Q3/Q4 (kicker of 2/3/4 doesn't matter unless there is two of them on the board) played like J9. And the higher connectors like JT played like Q5. That make the differenciations between Q3 & Q6, and JT from J8 way more obvious. And if any card between Q/J/T/or the low kicker come in the board, then someone will hit a pair and you will be fine. And if no one touched anything, you need to correct your position river. But all of that while I still believe personnally is good, has the 'upside' of adding more chaos to the game, and make conventions less effecient.
x) One of the reason why this convention come back is that if two players Alice and Bob fight for 6, and at the same time two players Cathy and Donald fight for high 5, you could end up with Cathy taking 4, and Donald taking 5 and waiting.
Then finally Bob abandon, let Alice have their 6, and pick their 5. If Donald play well, they will not ask 5 anymore, but now how strong is Cathy's hand? Does she pick 4 because she saw the fight between Alice and Bob and show strength, or does she goes down because she is weak?
And now Emily after their break come back, and oh she is 4.
She doesn't read the logs, and just take chip 4, to tell their ranking. But is she a strong 5 and assume she is above Cathy and Donald, or is she just a 4?
To know that, Cathy decide to give a call to Emily: she take token 5, put it back in the middle, and take Emily's 4 to show to Emily that she was initially 5, and it seem Emily should take a lower token.
All of that is working only if you put some value on the initial chip taken, and you can give call to others depending of your first chip taken, whatever you use strict conventions or not.
If you start to put lots of value on what happenned before, you ask for everyone included those which are late, to look at the whole log, before taking their first chip, which just seem so much worst.