What to expect from permitted_uri_characters

[eluser]c77m[/eluser]
[quote author="Cristian Gilè" date="1294960121"]base64_encode[/quote]

The data is already utf-8 encoded, which is friendly to the database, filesystem, and webserver. Agreed that I could encode all sorts of undesirable information into the URL, but I prefer to understand how permitted_uri_characters are intended to relate to allowable parameters.