Once you get used to tools like `go fmt` or Perl::Tidy it feels barbaric not to be able to cleanly format all your code instantly. Read only linters are nice but something that can reformat code is much nicer.
http://clang.llvm.org/docs/ClangFormat.html http://www.irill.org/videos/euro-llvm-2013/jasper-hires.webm
It's powerful, fast and will most likely be the base for a lot of {h,l}inting in editors/IDE's moving forward.
edit: Somehow missed that they mentioned Clang not being mature enough when starting this project.
I suppose the distinction is that they are not built in.
So: a formatter will, for example, make sure your lines are indented to some standard amount of indentation, a linter will bitch if they are not, and both the formatter and the linter should DTRT when they identify certain indefensible coding practices.