1.) the issue about countermagic

2.) the false  claim that a haxblade weapon is, itself, magical

What do either of these things have to do with the argument though? Again are we or are we not arguing about whether Hexblade warlock is equivalent to Kensei monk?

A Kensei monk can use a magical weapon and they don't stop being a Kensei monk. A Hexblade warlock can swing a non-magical sword but that doesn't make them stop being a Hexblade warlock.

Also are you arguing that flavour text does or doesn't matter? I thought you were arguing flavour text doesn't matter. In which case, why do you think the Hex weapon is the defining feature of Hexblade warlock? It is only one half of one feature of the subclass, and isn't particularly unique - any warlock can use Pact of the Tome to pick up Shillelagh to use CHA for their weapon attacks (Druids, and Clerics can get it as well). There is nothing in the subclass that makes the Hex weapon at all special beyond that one half-feature. 

In contrast Hexblade's Curse is a unique ability with 3/6 subclass features dedicated to it. It is HBC that is really the defining feature of the Hexblade subclass.

Even if you do consider the flavour text, this is the flavour text for Hexblade Warlock (emphasis added by me):

You have made your pact with a mysterious entity from the Shadowfell — a force that manifests in sentient magic weapons carved from the stuff of shadow. The mighty sword Blackrazor is the most notable of these weapons, which have been spread across the multiverse over the ages. The shadowy force behind these weapons can offer power to warlocks who form pacts with it. Many hexblade warlocks create weapons that emulate those formed in the Shadowfell. Others forgo such arms, content to weave the dark magic of that plane into their spellcasting.

Flavour-wise, Hexblade doesn't really have much to do with using weapons. The flavour text out right says there are Hexblades that don't use weapons at all and instead are pure spellcasters. There is more "blade" in the name of the subclass than any thing else associated with it.

My claim was that the Hexblade captures the concept of the Kensei well - which it does.

How does it though? I certainly don't see it. I'm simply trying to understand what your argument is. You were arguing that flavour doesn't matter only mechanics does so I posted about the mechanics. Now you are arguing the mechanics don't matter the "concept" does? Moving the goal posts much?

But even at the concept level what in specific is your argument - rather than just "because I said so" -  because as I see it:

The concept of the Kensei is a martial artist that can use weapons better than anyone else and in ways that nobody else can.

The concept of the Hexblade is a spellcaster that curses their enemies and can choose to use a weapon.

What part of Hexblade supports the concept of "martial artist"? What part of Hexblade supports the concept of "can use weapons better than anyone else"?

Unless Hexblade takes the Pact of the Blade they are awful at using weapons. So is it Hexblade that makes a warlock good at using weapons or it is Pact of the Blade? I remind you, the flavour text of Hexblade even says they don't need to use a weapon at all. Indeed, I've played with multiple Hexblades that hardly ever used a weapon.

The "Hex weapon" isn't even special, it's just a mundane ordinary weapon. And Hexblades are worse at using it than a Fighter or a Rogue or a Barbarian or a Paladin or a Ranger. Nothing about Hexblade makes them particularly good at using weapons in the general context of D&D. Sure they are the best warlock at using weapons but that's not saying much since warlock is very much a subpar / mediocre weapon user.

I think one could argue there is a similarity between the two if you view it as "A character who has a special relationship with a weapon and is good at using it", like, I can see certain character concepts which would fit both the hexblade and the kensei, depending on which aspects of the archetypes you wanna lean into.

That said, when I think Kensei, Im imagining the heroes of kong fu movies, wielding their weapons with superhuman skill and grace, Im imagining someone who truly uses their weapon as a natural extension of themselves. Its all about fighting dressed in a fancy flowing shirt or in a cool robe, doing acrobatics while effortlessly out fencing your opponent.

Needless say, a lot of that fantasy fits very well with the monk, since so much of the base monk class is also based on kong fu movies and I dont think it fits super well with the warlock.

On the bright side, it looks like the monk chassis will lead to a viable hammer/sickle combo dual wielder.