I noticed it shortly after commenting, and completely rewrote my comment accordingly. Excellent research! If you were to do a write-up on how you did this analysis, that would be very interesting (as the number of comments involved is large).
The "dev notes" in the top right links to https://intervolz.com/emdash-observer-writeup/
I downloaded torrents of reddit comments, and processed them in Go, written using AI assistance. Then Intervolz did this thing and wrote it up.