Time to start printing full yellow background instead of white. Con: lots of yellow toner needed. Pro: no tracking.
Or maybe never refill Yellow toner and then dots fail to appear.
Or maybe never refill Yellow toner and then dots fail to appear.
The person who wrote the list in the article mentions (at https://news.ycombinator.com/item?id=14502425, in this thread) that there is a second generation of this technology that doesn't produce microscopically-visible dots.
Perhaps the use of all available colors is involved.
However, I - and evidently many others in this thread - can think of many B&W ways to hide data in a printout.
By the way, if someone wants to take a stab at an older printer's firmware — many Kyocera printers from the late 90s and early 2000s used some small PowerPC with the firmware on a mask ROM on a SIMM-like module. Doubtful that there is anything protected there.