seems it's because of the last test in this line
if ( $postrow[$i]['user_avatar_type'] && $poster_id != ANONYMOUS && $postrow[$i]['user_allowavatar'] && $userdata['avatar_sticky'] )
the display of the sticky avatar is based on the current logged on user setting $userdata['avatar_sticky'] ?
It means if user X posts and has sticky avatar on. His posts will only be seen with sticky avatars if the other users have the sticky avatar feature on , and non logged one users won't see them at all ?
I'm not sure if it's meant to be like that.
I was more expecting it to be only dependant on the poster, if he has the sticky avatar on,
then the sticky avatars are shown for everyone, if not they are not
I'm not sure how to retrieve the current sticky avatar flag for the 'poster_id'
but I think that'd be the test to do.
For the moment I've just removed the last test.
It means that if a post was made by someone with the sticky avatar on, and that the person turns of the feature later on, the post will continue to show with the sticky avatars..
Not too much of a problem for me ..