I think the easiest way to test that specific behavior is to have a site where I don't have rep to see deleted posts; perhaps you create one, I load it and open the flag dialog, then you delete it, then I flag. And we see what comes out.
I can't create that situation on my own, I don't have any officially sanctioned sock (and if I had one that wasn't officially sanctioned, I wouldn't tell you in public anyway ;))
@bjb568 I'd rather it says outright that the post has already been deleted, actually. Make it obvious. But anything is better than an error that makes users think their ability to flag has been revoked :)
I'd like to go to bed, can we just test whether the error exists and then there can be a separate discussion about exactly how to handle the situation instead?
So it's something most likely related to non-customized flags. Which I guess makes sense, since even if a post has been deleted you can always flag for diamond moderator attention with a custom flag message, as long as you can see the post and its flag link in the first place.
It still deserves a better error message IMO :)
@BenCollins Do you think you have what you need for the moment? I'd like to go to bed. :-)