The “tribes” are easily identifiable on HN, it seems to me. For all of the most prolific HN posters, it is quite easy to predict which side of nearly any issue they’ll support.
Even then, the community is big enough that you're going to regularly run into comments from users you either don't recognize, or didn't realize were of the opposing tribe (or opposing-tribe-adjacent, let's say). So the shock experience never goes away. But I think you're right that it's most intense for less-familiar users, and that explains why there are so many people who use HN for a little while, inevitably encounter the shock experience, feel hurt, and leave. That's a common occurrence and which pains me personally.
The deeper point is that the site is designed to keep everybody together. It's not partitioned by friends or follow lists. There are no subreddits or social graphs. Design differences at that level are profound and affect everything.