I feel there are two very different things being covered here, although both are around avatars.
User avatars & 'System' avatars
User avatars are avatars assigned by the user. If enabled, users can manage their own avatars but only get a single one. This is stored via the user's forum profile. (Not site profile) Admin can also edit a user's avatar if need be.
System avatars are avatars assigned by forum admin. These are the ones like you see here, DNN Core Team, MS MVP, etc. The actual user cannot edit unless they are a forum admin. Unlimited # available.
In Forum versions up to 3.20.9, this capability is built in but had some serious bugs due to Gallery integration. In Forum 4.4.3, this was completely re-written and doesn't require the gallery. Seems to be working pretty well so far.
Display Avatars in Threads View
This take a user's avatar and show it in threadview. (This is what you see in the screenshot from here: http://www.bluishkarma.com/test/sample3.jpg)
This is not available in any forum versions available. I don't see this happening unless the forums integrate their own skinning/templating engine, which I have been considering for a future version.