Where would one be able to find out what these countermeasures are? Unless you're involved with the operation of HN, how would you know?

dang has mentioned the behind-the-scenes workings of HN a few times over the years, although finding them in amongst all of the other comments might be a bit of a slog: https://news.ycombinator.com/threads?id=dang

There is a surprising amount of manual intervention going on when it comes to what appears on the front page, for example. This was discussed a few days ago IIRC but I can't find the relevant comments now.

2nd chance queue.

https://news.ycombinator.com/item?id=19862701#19871817

Tracked down through Algolia:

https://hn.algolia.com/?query=second%20chance%20submissions&...