That is incredible, thanks for sharing. For others trying to find it, it's "herrmann2", not herman2. To try it yourself, the following worked for me in WSL:

  wget https://www.ioccc.org/2001/Makefile
  wget https://www.ioccc.org/2001/herrmann2.c
  wget https://www.ioccc.org/2001/herrmann2.cup
  wget https://www.ioccc.org/2001/herrmann2.hint
  wget https://www.ioccc.org/2001/herrmann2.ioccc
  cat herrmann2.hint    #instructions
  make herrmann2
  ./herrmann2 < herrmann2.ioccc

My mind is boggled. I get the basics of how autostereograms work, but the fact that it works so well with ASCII text is mindblowing.

Edit: If you're lazy, I made a quick Gist that does the above, so you can just do

  curl https://gist.githubusercontent.com/justusthane/a8c27c72350793ac452b86cc665a268b/raw/72aa6bf37689ea0cbbb70fa70fbd758c3a1fde3a | bash

(Obligatory "It's not safe to pipe internet stuff into a Shell" disclaimer)