Do the terms of the license allow for this kind of abuse?

Just because something is CC doesn't mean you can do whatever you want with it.

Yes, they do; it's not abuse when you're given explicit permission. CC BY-SA means you can do whatever you want with it as long as you attribute the source as specified.

"as long as you attribute the source"

danielbarla said that they presented the material under a false name; this goes beyond copying and becomes plagiarism, which I can't imagine is an intended result of the CC license.

Is the source 'User X' or 'StackOverflow'? When you reference CC BY-SA code you don't reference the people who, say, checked it into git but rather the whole repo.

CC BY-SA is short for Creative Commons Attribution Share-Alike. BY means you must attribute, and SA means you must license any distributed derivative works under the same license (copyleft). Attribution on its own is not enough.

No, attribution is required.

Interesting, from the file sizes you can quickly gauge the relative popularity of each subject.