More than you think. But I think more would call themselves "spiritual" or "unaffiliated religious" than be members of organized religion. I have no peer-reviewed evidence for that though, it's just a personal observation.
regardless of being "religious" or not, the bible is fascinating!
Even more interesting, I wonder what all the demographic indicators are for HNers.
Male/Female/Trans/Nonbinary/Other, race, religion, age, industry, occupation, etc.
I know it's kinda hokey/a little reddit esque, but a "HN Demographic Survey" would be cool.
There's a good number of religious users. I'm not Christian, but I think Bible commentary is fascinating. Things like linking a few words to a whole database of knowledge. It doesn't apply to things that aren't scripture.