I'd tend to agree with the parent that multi-pthreading is a poor abstraction but I'd add an important note: only systems programmers should be explicitly spinning up pthreads. Explicit pthreading is a poor abstraction for everyone else. Application programmers are probably operating at the 'wrong' level and greenthreads make more sense.
Real threads are great for implementing things like clojure's core.async or task systems like Intel's Threading Building Blocks. Both of these are super useful and don't work as well with processes instead of threads. I definitely agree that most programmers shouldn't be using threads directly, but they should be available as a building block for higher level abstractions.
