The only language I've seen pipe used with comments (not line comments though) is Common Lisp:

  #|
    This is a multi-line comment
  #|
    And they can be nested because this is really just a reader macro
  |#
  |#

I don't think I've ever seen a standalone | for comments, especially since it's so often used as bitwise or logical or.

And here they use \ for bitwise or, and the word `or` for logical or.