Seconding. Sending back the whole page on AJAX upvote seems unnecessarily wasteful, and sounds like something trivially fixable.
Taking data from 2.5 years ago[0], HN has ~300k daily uniques. Assuming 10% of that are users, each upvoting one story, that's 30k unnecessary page renders per day. That's ~2% of the total views (though the more expensive views - AFAIK when you're logged out, you get cached pages?), so on the one hand it's not much, but on the other hand the fix should be trivial and have minimal impact on code readability.
Taking data from 2.5 years ago[0], HN has ~300k daily uniques. Assuming 10% of that are users, each upvoting one story, that's 30k unnecessary page renders per day. That's ~2% of the total views (though the more expensive views - AFAIK when you're logged out, you get cached pages?), so on the one hand it's not much, but on the other hand the fix should be trivial and have minimal impact on code readability.
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[0] - https://news.ycombinator.com/item?id=9220098