literary masochist
Ideally, make it so the system silently skips over any avatar share (on an individual avatar level, not the whole batch of shares) that would cause a duplicate in the destination gallery. So we don't have this problem in the first place.
This "faculty lot" you speak of sounds like a place of great power...
Literally A Princess
I thought of that, but I didn't know if it would be more work to program than simply letting someone delete a duplicate.
Heapers’ Hangout
literary masochist
Hence, "ideally". 
I've been meaning to raise this for a while but never got around to it; there are at least two duplicates that I have left alone for ages because of this thing
Well, a possible workaround in the meantime may be: share one of the duplicates to your sockpuppet, delete both from the main account and then share back.
Though only worth it if you really want to keep your gallery duplicate-free 
literary masochist
Or another troper, if you're somehow allergic to sockpuppetry.
This "faculty lot" you speak of sounds like a place of great power...
Is this still an issue?
"For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." - Richard Feynman
Seems like not, so closing. If it is please ask on Query Bugs.
"For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." - Richard Feynman
Admittedly minor complaint, but: If, for whatever reason, you are sent the same avatar more than once, attempting to delete the duplicate from your gallery removes both instances of the avatar, instead of just the one.
Could this behavior be changed?
Heapers’ Hangout