Remind new wiki users to put some contact info on their User Page

When creating new accounts on https://wiki.debconf.org/ the new user should be automatically reminded to put some contact info on his User Page.

For instance,
https://wiki.debconf.org/wiki/User:Jidanni leads the reader to full contact info.
https://wiki.debconf.org/wiki?title=User:Kaare&oldid=23284 on the other hand doesn't.

Why is this important? Well some users might sign up for various things on the wiki, but we have no way to contact them if there is a change of plans, and they don't monitor their wiki watchlist.

I can't find the right place to file this bug so am filing it here.