I believe we've sorted out the security concerns for avatars, I have re-enabled them.
In the past, we allowed users to specify a URL for their avatar. This option is still not enabled for security reasons. Instead, your only option for avatars is to upload an image, with max dimensions of 120x120.
All existing avatars were cleared for safety's sake. I apologize if that inconveniences anyone.
Please keep avatars to a PG-13 rating.