68k users have used the favorite feature, on 1.7M posts. It's not widely used by HN standards, but that's certainly not "almost no-one".
You can also gauge it by how many people rushed to this thread to post "please don't remove the feature" when someone mentioned we had thought about removing it.
Follow up questions when you want to measure adoption:
- 68k users out of how many users on HN? This is the metric that really matters when you want to consider how wide the adoption is.
- Number of users may not be very easy to evaluate as there's throwaway accounts, inactive accounts and the like, so ideally you would need to account for the people who log on at least once every month or something.
- Among those, you would need to filter those who actually use the feature regularly vs the ones who just used the feature once and never used it again. Look like the average is at 25 per user based on the data you provided, but I am guessing there are users with 100s of favorites so that means there are people at the end of the tail as well, with just a few, which should not be counted as "active favorite users".
By the way @dang, is there any hidden function on HN to see some HN related stats?
You can also gauge it by how many people rushed to this thread to post "please don't remove the feature" when someone mentioned we had thought about removing it.