This issue was originally raised in the mailing list thread starting here:

  http://mid.gmane.org/<88fbcdc8c72a486386b3b02ab20e88bd-mfwitten@gmail.com>

In `makepkg', specifically:

  https://projects.archlinux.org/pacman.git/plain/scripts/makepkg.sh.in?id=912ea363dec9038e9226a619364e16709720cac3

the following exist:

  	local provides_list=()
  	eval $(awk '/^[[:space:]]*provides=/,/\)/' "$BUILDFILE" | \
  		sed -e "s/provides=/provides_list+=/" -e "s/#.*//" -e 's/\\$//')
  ...
  	local backup_list=()
  	eval $(awk '/^[[:space:]]*backup=/,/\)/' "$BUILDFILE" | \
  		sed -e "s/backup=/backup_list+=/" -e "s/#.*//" -e 's/\\$//')
  ...
  	local optdepends_list=()
  	eval $(awk '/^[[:space:]]*optdepends=\(/,/\)[[:space:]]*(#.*)?$/' "$BUILDFILE" | \
  		sed -e "s/optdepends=/optdepends_list+=/" -e "s/#.*//" -e 's/\\$//')
  ...
  	local known kopt options_list
  	eval $(awk '/^[[:space:]]*options=/,/\)/' "$BUILDFILE" | \
  		sed -e "s/options=/options_list+=/" -e "s/#.*//" -e 's/\\$//')

Perhaps there are more.

As you can plainly see, this ruins the ability to include comments that use
the `)' character, as in the following:

  options=(
    '!strip'
    '!makeflags' # Apparently, there are issues with concurrency (`-j2', etc.)
  )

As explicitly pointed out by contributor lolilolicon, it also ruins seemingly
valid usages of the `#' character. For instance:

  optdepends=('hashtag: A program that parses #hashtags')

Perhaps there are other ramifications.