I feel that community wiki questions and answers feel soul-less compared to their authored counterparts.
Have a look at this Community Wiki question posted by Jeff. The majority of these posts are by one or maybe two people. It would be nice to see who was involved in those edits.
So, I propose, instead of showing no gravitars, show multiple. Show the most recent 2-4 people that have edited the post (Or, to stay consistent, the people with the highest percentage of content). For example:
This will give Wiki posts more life without destroying the idea that wiki posts are edited by the community.