alt Hacker News700 is actually a pretty good sample size unless you are looking at some tiny crosstab, or there’s some skew (which you won’t naively scale your way out of anyway).
It is also interesting to note that the comparison is between recent comments and recent comments by new users. So, I guess this would take care of the objection that em-dashes (a perfectly fine piece of punctuation) have just been popularized by bots, and now are used more often by humans as well.
Maybe there is a bot problem. Seems almost impossible to fix for a site like this…
I think what a larger sample size would do would be to help capture changes over time. Humans tend to be more active certain times of days, whereas bots don't tend to do that.