[kremi]

Checks are quite foolproof too - spelling out the number (a hundred eighty eight) and writing the number (188), like on checks.

The paragraph you mention seems to worry more about mistakes more than tempering attempts though (taking 10x the dose prescribed could indeed be problematic)

[HPsquared]

The important part there is the termination characters. "Dollars" / "Pounds only" etc. and the decimal point (though that's easier to turn into a comma and make into thousands... Funnily enough the German way of using comma as the decimal separator avoids this)

[kijin]

Yeah, we've tried null-terminated strings and it wasn't fun. Better use a more explicit, highly visible character.

[miki123211]

Polish still regularly does this for contracts and all kinds of legal document.

I regularly see verbiage like "person A promises to pay person B 100 (in words, one hundred) zloty upon termination of this contract."