For this purpose we can use sticky posts. Users who actually google your forum (=sites with a lot of information or solutions for common problems) have no idea about who is “official”. Good examples for forums which I visit frequently without even having an account are:
So, if I am trust user level 4 and I trink coffe every day with the staff it’s fine. If I just google the forum the avatars are not quite helpful. After I switched from a bulletin board to discourse a lot of my users claimed that it is really confusing. After I went into more detail I found out that it is just too much (maybe redundant) information on the topic list for them.
As above. Most people won’t know your avatars (and avatars may change over time) so they will just ignore it.
May contain useful information 
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I just recognize sam and your avatar. But support and hosting topics also have a support category :).
So in my opinion these avatars are just a little bit clown vomit.