This info might help:

I have a mailto URI spec page at <http://shadow2531.com/opera/testcases/mailto/mailto_uri_scheme_idea.html> (old page is at <http://shadow2531.com/opera/testcases/mailto/modern_mailto_uri_scheme.html> and has more text-based parsing rules instead of just JS examples, but the parsing is a little out of date on that old page).
 
On that page is a "consuming" section that may be of interest to your mailto URI research. The consuming rules are very web-compatible. There is one issue mentioned in the "Converting the URI to a dataset" section with "#" though. Basically, my findings in <http://lists.w3.org/Archives/Public/public-iri/2009Oct/0030.html> for the "mailto:test#abc" case might be incorrect (even though no one disputed it).
 
I also have a post here <http://lists.w3.org/Archives/Public/public-iri/2009Sep/0013.html> that's based off Opera bug CORE-36435 (mentioned in DSK-263481 and worked around by mail.ru devs) that Opera still has today.
 
Also mentioned on my mailto URI spec page is <http://shadow2531.com/js/mailto_uri_parser.js>. It's based off of my spec and is used in production in <https://addons.opera.com/en/extensions/details/gmail-compose/?display=en>. There's also <http://shadow2531.com/sm/html5_mailto.php.zip> that's based on those rules and is used to make SquirrelMail accept what HTML5's registerProtcolHandler emits.
 
Also, there's <http://shadow2531.com/opera/testcases/mailto/MailtoURIParserPack.zip> that's mentioned at: <http://shadow2531.com/opera/testcases/mailto/modern_mailto_uri_scheme.html#implementations>.
 
"In MailtoURIParserPack.zip are C, C++, D, Java, Javascript, Perl, Python, Ruby, Pike, Lua, Tcl, PHP5 and Python3000 MailtoURIParser classes that use the rules in this document to show examples of parsing. The test above uses a Javascript version to parse the mailto link to generate the form data."
 
Those implementations in the pack are outdated, but they're still useful for the general idea of parsing mailto URIs.
 
On a side note, the reason that I made my own mailto spec is that my suggestios for error handling in the mailto RFC were rejected as being out of scope.