On a users profile page, clicking their avatar should enlarge it like it does on twitter, instead of linking to their homepage that you're already on.
I've added that to our list of things to ask the developers. It's not a high-priority issue, but I do find it useful. Different sites handle it differently - Facebook, for example, pops up a post that has comments whereas Twitter just pops up the cropped image.
We're currently looking at other features to implement with avatars, as well; we may include the ability to choose an avatar from your previously uploaded pictures. Once we know how we'll do that, we'd have a good idea of how to implement enlarging avatars and if it's practical.
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