A couple observations on fragmentions (https://indiewebcamp.com/fragmention):
Google Drive has a comparable feature which uses this syntax to bookmark searches: https://drive.google.com/a/gonze.com/#search/%lorem%20ipsum%22
Another piece of prior art is the .well-known: http://www.mnot.net/blog/2010/04/07/well-known http://www.rfc-editor.org/rfc/rfc5785.txt
I think that what the RFC 5785 example shows it that Kevin's double-hash syntax is one of a thousand flowers blooming. It's the same process that played out eventually as .well-known - a path to standardized fragment IDs.