The linked thread shows people talking about a US regulation that requires printer makers to produce stegonographic tracker dots on every page printed

Can anyone cite the statute?

I suspect they are talking nonsense. Everything I have read on the topic mostly conceals the motivation of the printer makers. But my speculative impression is that the US gov secretly requested the feature and the printer makers were happy to accommodate because it leads to selling more yellow inks and toner. Plus it gives them a “good excuse” for blocking color printers from printing black docs when any of the color cartridges are empty.

But in any case, it would be interesting to get some concrete information about printer makers’ motivations. Why haven’t they been interviewed by the EFF?

UPDATE: someone suggested EU Directive 2014/62. But AFAICT from the wording that directive does not seem to force printer makers to watermark documents.