Are trains stopping between stations to let passengers board/alight just a Canadian thing?

To build on Kate's answer, Wikipedia also mentions that this practice is possible on the Alaska railroad. There are also a number of flag stops on the Amtrak train network in the US. Flag stops are fixed locations in which the train will only stop if there is a passenger waiting and/or if a passenger wishes to depart.

I want to say that there's some lines out in the Siberian and Far Eastern stretches of Russia that allow you to do that, but I cant' seem to recall where I got that information. Outside of that nope, never heard of such things outside of Canada.

Officially, such a thing certainly does not exist in Sweden.

But, if you are in the far, far north, north of the Arctic circle, far out of sight of anyone with an office or otherwise a care for such details as rules and regulations, and only if you have friends in the right places (such as in the cab of the train) and travel when few others are travelling…:

Early summer, somewhere in the area around Kiruna.

There is a cabin along the railway here, formerly used by a railway employee but now privately owned.

Later, a local friend told me he had sometimes phoned his friend at traffic control so that a train could pick him up or drop him off at some remote stretch of railway. He told me they'd do it for others as well (secret grandfathered policy) but I never tried. Only along the northern parts of Malmbanan, between Gällivare and Abisko or so.

On top of that, I suspect it's also quite possible on the Inland Line, a line that now only has trains for tourists and only in summer.

For what it's worth, this is only really available on the Sudbury-White River (formerly Lake Superior) route on Via. Having used this to traverse the north quite often when I was younger, it was not unusual to see people alight from various locations that weren't stations - including with quads or watercraft. (Usually canoes).

This is indeed a thing, and very neat.

I've seen this on the Polar Bear Express between Cochrane and Moosonee, Ontario, though that is an Ontario Northland train rather than Via. Virtually all the "stations" between those two are flag stops that seem to exist solely for ticket pricing purposes, the few people not travelling the whole distance got off elsewhere.