Absolutely.

And nothing advances your career quite like getting your employer into a multi-year legal battle and spending a few million on legal fees, to make some images 20% smaller and 100% less compatible.

Well, lots of things other than JXL use ANS. If someone starts trying to claim ANS, you'll have Apple, Disney, Facebook, and more, on your side :)

But that doesn't matter. If a patent is granted, choosing to infringe on it is risky, even if you believe you could make a solid argument that it's invalid given enough lawyer hours.

The Microsoft patent is for an "improvement" that I don't believe anyone is using, but Internet commentators seem to think it applies to ANS in general for some reason.

A few years earlier, Google was granted a patent for ANS in general, which made people very angry. Fortunately they never did anything with it.

I believe that Google's patent application dealt with interleaving non-compressed and ANS data in a manner that made streaming coding easy and fast in software, not a general ANS patent. I didn't read it but discussed shortly about it with a capable engineer who had.

If the patent doesn't apply to JXL then that's a different story, then it doesn't matter whether it's valid or not.

...

The fact that Google does have a patent which covers JXL is worrying though. So JXL is patent encumbered after all.

I misrecalled. While the Google patent is a lot more general than the Microsoft one, it doesn't apply to most uses of ANS.