Copying and pasting the following into Discourse:
For secure messaging and calls connect with me over Snikket/XMPP at xmpp:maiki@chat.v2.talkgroup.xyz.
Produces (with xmpp added to allowed href schemes):
For secure messaging and calls connect with me over Snikket/XMPP at <a href="mailto:xmpp:maiki@chat.v2.talkgroup.xyz" dir="ltr">xmpp:maiki@chat.v2.talkgroup.xyz</a>.
The href="mailto:xmpp:maiki@chat.v2.talkgroup.xyz" is the issue in this case. Noting as a use case for this bug. 