The way you word the statement and then append "Curious." makes it somewhat hostile. It's a callout, not just an observation.

"I'm curious why you say you're 'very much' in the WWW camp but you don't use it on your own site." would not have the same tendency to register as an attack.

That's just a comment written in a second or two, not a verse from the bible. No need to dissect it this deep. If this is hostile, asking "how are you" is too, implying one may be in bad shape.

If it's a comment written in a second or two, is it worth posting? It was definitely a call-out as indicated by the finality of "Curious"; it could have been asked very matter-of-factly if he was actually curious.

As a contradicting opinion, by my conversational standards, the comment reads as just an observation that this is curious, and an implication that the poster would be interested in more information. It does not read at all like an attack to me.

Some/Many posters here are not native speakers. There's no English conversational standard on the Internet.

Yes, that's why I was explicit that I was discussing my personal conversational standards that reflect my personal history, which is different from yours. As you point out, there are people from a wide variety of backgrounds on the internet, and part of participating in the internet is understanding this and expecting it.

When you see something that you might think is hostile, it's often more productive to give them the benefit of the doubt and presume that they intended good faith but have different conversational norms from you. In the best case, they meant well, and everything proceeds nicely. In the slightly worse case, they didn't mean well, but you've helped de-escalate, and things are back on track for a nice discussion. In the worst case, they get more blatant in their attacks, and at least you'll find out that productive discussion wasn't possible anyway. Not much downside, and lots of upside, in my experience.