Agree, if you do it, there is no harm in doing it right. However, I grew up with the metric system and I’ve never seen capitalization of the prefixes being a mistake that happens in the real world. I.e. your ADC can measure up to 500 mV and you instead ‘accidentally’ put 500 Megavolts through it. That is somewhat unlikely to happen. But then mistakes like that do happen. People wanting to order 500 rolls of toilet paper and getting 500 shipping crates of it. Things like that definitely happen. Especially in combination with computers that just do whatever you typed in. I’d just not call it ‘common’.