OT: Where did URI pipe symbol hack originate?

[Jeff Lowery <jlowery@scenicsoft.com>]

As is used after Windows drive letters:

file:///C|/mydir/myfile.txt

Having a little debate about whether the appropriate thing is to escape the
colon with %xx instead of using the pipe (or colon).  Has a consensus formed
that is (mostly) cross-platform compatible?