Memory Parity Error: A Few Questions

I've been reading a bit online about those so-called memory parity errors. Wanted to throw around a few (hopefully not too noobish) questions:

-Related issues have always been resolved by changing the RAM or mobo (hardware), changing settings (BIOS), or updating drivers (software). In your experience, what's the most common cause?

-An old article makes a distinction between non-parity and parity memory. It concludes that parity was deprioritized in the late 90s, early 2000s, but is starting to become prioritized again. Is this true?

-If the last statement is true, can I assume that practically all RAM sticks sold are parity memory? And is there an advantage in ensuring that you're using parity memory?

-Lastly, how can I tell if the RAM I want to buy if parity/non-parity?

Price and data sheets will tell you.

I also do not worry about parity errors in my computers. I do work with high reliability military systems that will correct a single bit error instead of just flagging it as a parity error. But the hardware to do that is pretty complex and expensive.