Thanks! Here are the ones I found that have comments, plus a few others:

Why printers add secret tracking dots (2020) - https://news.ycombinator.com/item?id=26526035 - March 2021 (3 comments)

DEDA – Tracking Dots Extraction, Decoding and Anonymisation Toolkit - https://news.ycombinator.com/item?id=17392977 - June 2018 (7 comments)

Why printers add secret tracking dots - https://news.ycombinator.com/item?id=14505444 - June 2017 (100 comments)

Printer Tracking Dots Back in the News - https://news.ycombinator.com/item?id=14504833 - June 2017 (1 comment)

List of Printers Which Do or Do Not Display Tracking Dots - https://news.ycombinator.com/item?id=14501894 - June 2017 (210 comments)

Secret Dots from Printer Outed NSA Leaker - https://news.ycombinator.com/item?id=14494818 - June 2017 (211 comments)

Printer dots raise privacy concerns - https://news.ycombinator.com/item?id=245963 - July 2008 (13 comments)

Thank you for putting the title and date in there.