Hi Malcolm.
I've been running standard (black) thermal paper through my HP's without any difficulty. I suspect that, "paper is paper", and I don't see how a print head could tell whether it is heating up black paper or blue paper. This is just my opinion. Maybe the paper was smoother, but I can't imagine that black paper is more abrasive than blue paper.... and I don't see how the thermal properties could be that different.
I did hear that every division of HP lost money last year except for its ink, paper, and toner division, which made billions of dollars and made up for all of the other divisions' losses. I've also heard that HP loses money on their printers, but makes it up many times over with ink sales. (Thus, giving away the razor and selling the blades...) I'm sure that's why they caution so strongly against using anything other than their brand, though I've been refilling ink since the Thinkjet days with no problems, other than not having the ability to fill in a vaccuum and then have the ink expand into the channels of the cartridge in a nitrogen atmosphere.... a guy who sells ink refills for a living tells me the best way is to fill cartridges and let them sit a few weeks, rather than using them immediately... but that's another topic. HP has begun using "smart chips" to deter refilling, but I've kept my HP 2000C's running for years by refilling.
So, my guess is that they were trying to scare people into just using their paper.
Anyone had any trouble with "standard" thermal paper?
Michael