Well, I can only speak for myself here- I'm personally familiar with Cartesian coordinates so and x and y are locked firmly into my brain. Cz and Cy are not. At this point, what's easier on my brain is reading anything that's as close to english as possible- not reading letters, and then having to translate those into english. I have a lot to remember as a beginner! ;) Do you know how long its taken for me to accept that 'i' is okay in loops? It's a silly letter that is always chosen because of programming tradition, more or less... so when I originally saw 'i', the first thing I thought of wasn't a temporary variable.
I'm sure people not used to the Cartesian coords must feel the same way about x, y and z. So, the easier you make things for the beginner, the less our poor little brains have to worry about while trying to learn all the other stuff :)
McConnell in Code Complete lays out some good foundations for variable names. If you name them well, your code can often be easy enough to read that other people won't be screaming for comments. I'm sure it also comes down to a personal thing for your own code, but if you're going to share it with others, or try and teach someone with it, the more explanatory you can make it the better.
I'm sure people not used to the Cartesian coords must feel the same way about x, y and z. So, the easier you make things for the beginner, the less our poor little brains have to worry about while trying to learn all the other stuff :)
McConnell in Code Complete lays out some good foundations for variable names. If you name them well, your code can often be easy enough to read that other people won't be screaming for comments. I'm sure it also comes down to a personal thing for your own code, but if you're going to share it with others, or try and teach someone with it, the more explanatory you can make it the better.