> Mine also isn't anywhere nearly as confusing as his by default

You can run the following and try it for yourself. Don't forget to highlight some text before right-clicking an image (e.g. https://en.wikipedia.org/wiki/The_World_Factbook)

  TMPPROF="$(mktemp -d /tmp/ff-tmp.XXXXXX)"
  /Applications/Firefox.app/Contents/MacOS/firefox -no-remote -profile "$TMPPROF"