When writing CSS, is there any reason to prefer shorter, more elegant selectors over longer, more comprehensible ones? I'm looking for technical, not personnel, reasons – processor hits and whatnot. There are often many ways to select the same element(s), and I'm unclear what, if anything, might be best practice.
You may want to have a look at the Block Element Modifier methodology http://getbem.com/
No matter what methodology you choose to use in your projects, you will benefit from the advantages of more structured CSS and UI. Some styles are less strict and more flexible, while others are easier to understand and adapt in a team.