@ThomasWard I think novices may read
the first paragraph there as saying that Linux systems can't circumvent Unix-style permissions on external storage, not realizing root can always get around them (on a normal device), that UIDs and GIDs may not match up across systems, etc. I know you're probably trying to keep it simple, but would you be willing to make clearer that the main issue is that the OP doesn't
control the systems that will use the device? Maybe: