Oh so that’s it! I use GNU parallel a lot, and installed moreutils yesterday, and parallel seemed to behave a bit… different. Couldn’t quite understand why, as I didn’t expect moreutils to replace parallel when you install them.
I'm sorry, what? First, moreutils package installs its parallel as parallel-moreutils. Second, pacman (like any other pm) wouldn't allow overwriting files belonging to other packages.
I’m using Arch, btw.