I wonder whether whether it’s possible to render this effectively useless in software by just adding more yellow dots to the image.

Like, can I just cover every non-yellow pixel with a yellow pixel at the same intensity as the tracking dots have? Yeah, maybe it gives my image a faint yellow cast, but…

EDIT: Yup, apparently it is.

https://en.wikipedia.org/wiki/Machine_Identification_Code

Protection of privacy and circumvention edit

Copies or printouts of documents with confidential personal information, for example health care information, account statements, tax declaration or balance sheets, can be traced to the owner of the printer and the inception date of the documents can be revealed. This traceability is unknown to many users and inaccessible, as manufacturers do not publicize the code that produces these patterns. It is unclear which data may be unintentionally passed on with a copy or printout. In particular, there are no mentions of the technique in the support materials of most affected printers. In 2005 the Electronic Frontier Foundation (EFF) sought a decoding method and made available a Python script for analysis.[20]

In 2018, scientists from TU Dresden developed and published a tool to extract and analyze the steganographic codes of a given color printer and subsequently to anonymize prints from that printer. The anonymization works by printing additional yellow dots on top of the Machine Identification Code.[1][2][3] The scientists made the software available to support whistleblowers in their efforts to publicize grievances.[21]

That makes it even more annoying. If printer manufacturers aren’t going to defeat that, I’d kind of rather that they not have the yellow dots at all.