On a wiki, we EnlargeSpace by convention to create namepages, where we normally leave personal messages. It helps if people have a namepage, of course. In this case, the namepage serves as a MessageBox. Since most of us are vain, or at least highly protective of our FrontLawns, or even extremely sensitive to seeing our names, it is expected we will notice changes to our own namepages on RecentChanges.
On most sites, e-mail is in fact the de facto MessageBox. Interestingly, even though many participants have elected to post their e-mail addresses, most personal communication on a wiki is done in public through the namepages. It's one part OpenProcess and another part comraderie. Why leave the party just to ask a question? It's rude somehow, don't you think?