He's a supernatural being children are assured is real and encouraged to believe in, and give offerings to like a household god, and who is supposedly rewarding or punishing their behavior based on his infallible moral authority and omniscience.
It's probably not religion in the sense that anyone actually worships Santa, but he does qualify as a religious figure.
No, but I think the suggestion of the post you replied to is that one fanciful being that people convinced you existed, might encourage you to think critically about other beings instead of simply accepting their existence because people tell you they are there.
The concept has definitely been affected by religions, even having some roots there, but nowadays it's as religious as Easter Bunny. Saint Nicholas is God's earthly avatar: rewarding those who live by his rules and punishing the rest.
In NL the tradition has it that Saint Nicholas hails from Spain (he didn't he was originally from Turkey) and the 'Black Pete's' that you refer to are his helpers (can't have a Saint that's black now, can we...). There is a ton of hypocrisy at work there and there has recently been quite a bit of backlash. Predictably the anti-Europe sentimentalists seized on this to tell the rest of the world they shouldn't mess with our perfectly racist traditions.
The Moors (which the Black Petes represent) are an interesting chapter in the history of mankind in their own right, and were Muslims rather than associated with the Christian faith, to see them as helpers of a Christian entity must have seemed like a good idea at the time, but in the present it is less so.
This is likely also the reason why 'St Nicholas' hails from Spain for the Dutch because the Moors did in fact inhabit a chunk of Spain at some point rather than from Turkey where he actually was from, a country that the Dutch kids probably had trouble relating to before 1960, but Spain was a lot more visible.
The typical threat parents used to use to get their kids to behave was to threaten them with beatings by the Black Petes and if that didn't work out to be stuffed in burlap bags and taken to Spain...
It's probably not religion in the sense that anyone actually worships Santa, but he does qualify as a religious figure.