[dragonwriter]

It's political, so it's probably being flagged and demoted for that reason.

It's probably triggering the flamewar detector, and getting demoted for that reason.

There's probably no need for active censorship by the mods to explain the observed results.

[benlambert]

There was another submission that was on the front page half an hour ago with only a few comments (so no flamewar) and appears to have been directly removed by a mod: https://news.ycombinator.com/item?id=12724507

[EdHominem]

There's no read for "real" censorship if your algorithms take care of all the threads you'd find objectionable.

[sflicht]

Of course the existing moderation policy constitutes a background of censorship, so your claims should be evaluated within that contest.

[dragonwriter]

In the sense that all systems of deciding what to publish and how are censorship, sure.