I discovered that the new usergroup to which you were recently promoted was unintentionally set to not allow your secondary usergroup permissions by be stacked as we assumed they would, and many of the permissions were set to "No" including the ability to post, and to use avatars/signatures and other features. I have fixed that now so you should find all of the previous features you had restored.
I am very sorry this happened. You and GJA are the first "MHB Math Scholars" to have this usergroup set as your primary, and so this issue was never experienced by anyone before. The other users you mentioned likely do not have an avatar defined. I haven't checked their profiles in the AdminCP.