cutting off their nose

This alone makes it clear that this manifest is not at all arguing for completely ignoring merit. Instead it's based on the realization that merit cannot be measured objectively. This ties it back directly to DEI, because it's clear that we perceive contributions as more or less important not only on the contribution itself but also because of who contributed it. And there we do tend to value those higher that are more like us. So DEI is a way to _fix_ meritocracy, not to replace it.

I don't see why you're implying we should be surprised or outraged about that. It's saying we can't objectively measure "merit", because it's such a vaguely defined term that in practice it's usually twisted (intentionally or unintentionally) to mean "people like me". And even if we could measure it, we shouldn't judge people on that measurement, because open source communities are social groups of humans, and groups benefit from having a range of skills and viewpoints, and humans have value beyond their ability to write code, so we should embrace that value rather than dismissing anyone who doesn't fit our narrow objective criteria.

That seems entirely consistent with the Contributor Covenant: it says communities should be welcoming and respectful to all. It doesn't say this only applies to the objectively best C hackers. The kernel's CoC explicitly calls out "levels of experience", which will be a big part of any attempt to measure merit - inexperienced programmers will write poorer code, but the kernel says they should still be welcomed and respected. That lets them contribute to the project now, and gain experience and contribute even more later, which is pretty obviously a good thing for the group.

(Incidentally, the term "meritocracy" was coined in a satirical, dystopian novel, so it seems weird to hold it up as an ideal that cannot be criticised or improved upon. It has benefits over some other models, but it has always been an imperfect concept.)

In any case, I think Post-Meritocracy is a significantly different thing to corporate DEI and you shouldn't conflate them. Companies can't welcome everyone equally: a job opening will have dozens of applicants and they have to make binary judgments on who to accept, so there's an unavoidable exclusivity. The best they can do is refine their criteria to reflect what's actually good for the group (avoiding the simple, selfish criteria of "people like me"), and identify and minimise their biases when evaluating those criteria, and support the successful applicants to work as effectively as possible based on their individual needs, which are the processes that will be called DEI (and that the government gets upset about).

I refer you to xkcd #1357.

I wish fewer people would engage in this kind of knee-jerk reaction to someone expressing an opinion based on their experience that they disagree with.

We used to all be united by FOSS regardless of petty differences of opinion. It is sad to see that change.

I think you meant to say: "Decades-old DEI practices were rebranded by a specific political party in the early 2020s so it could be used as wedge issue"