Answer: How to avoid pop-up of *Async Shell Command* buffer in Emacs? rofl

The question was asked in 2012, and at the time of my writing, the most recent answer is dated 2015. Now, in 2017, I can say that the answer is simple:

(add-to-list 'display-buffer-alist
  (cons "\\*Async Shell Command\\*.*" (cons #'display-buffer-no-window nil)))