For the moreutils implementation of parallel:
I noticed that the first form of command does not use the shell:
parallel [options] [command] -- [argument ...]
I noticed that the second form of command *does* use the shell:
parallel [options] -- [command ...]
Please document both of these in the manual page, so that folks know
that they should not quote commands passed in the first form but always
shell-quote commands passed in the second form.