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Yes, currently we are using pictures provided by Facebook, there are plans to allow to change them in the future.
Then are not displayed in comments yet, this is under development right now.
And, I think community would be interested in all kins of tutorials. Just post one of them and see if it gets upvoted.

I just noticed my avatar has now become an anonymous silhouette, which I appreciate but it's unclear what just happened.

You server-side session might have expired or you logged in from another computer, we will make it smart enough to be pickup userpics when moving across devices.