MIght be another tricky one.
Many of the achievements I plan to give will be based on particular threads, sometimes single ones and sometimes collections of them. I’m guessing it would be very difficult to permanently attach links to achievements, like achievement “Great post!” for userA links to a different post than with the same “Great Post!” achievement for userB.
I was thinking though, maybe the link reference could just appear in the activity update (I’ve forgotten the BP lingo…). So when I’m here: there would be an “attach URLs” space there where I could insert URLs to be included in the activity update. So the update would go something like this:
@sadr unlocked “Great Post” , , 
The numbers in brackets being referral links that the admin specified for that particular user.