I think the definition of quiet time might be something do with Timezone bias and I don't know if HN has peak times and Quiet times - writing this from IST 4:29PM.

My concern was more of 'Tricking the system?'

Night time in the US (especially California) has always been a quieter time. I live in Europe and when I am regularly checking HN I can often tell when it's start of working time in the Bay based on the front page.

You can do a quick analysis but my observation is that stories on the front page during west coast night time are significantly more stale (submitted more hours ago) and/or with less points. Something getting near the top during that time with ~10 points is nothing unusual (especially if the upvotes happen this fast).

Edit: Also moderator intervention is a much more likely hypothesis than 'tricking the system' on average on HN, but this case is well within the norm so I wouldnt suspect that.

If it helps any it was posted just before lunch UK time (which is why I'm here, hello!)

bon appétit

The major quiet time is about 8am - 14am UTC. The difference is very pronounced