Hi,
When attempting to use XMPP URIs[1] in Dokuwiki, they get treated as email address, and prepended with mailto:
I developed a patch[2] a long time ago, which applies (just about) to 2008-05-05, I haven't tested later versions. I'm not claiming it is the best of code, but it works for me :-) Though perhaps it could at least serve as a base for an official fix.
An appropriate icon would be the XMPP logo[3] (without the text).
[1]:
http://wiki.jabber.org/index.php/XMPP_URIs
[2]:
http://matthewwild.co.uk/projects/code/dokuwiki-xmpp.patch
[3]:
http://en.wikipedia.org/wiki/File:XMPP_Logo.svg