What are we doing to flag/mark/deal with duplicate file entries?

Someone suggested we use "dupe" as a tag and then link to the other image.

On some other boorus they add the tag "duplicate", and also make the original its parent (i.e., put the original pic's number in the dupe's "parent" field).
Dunno if parenting works here, though.

Okay, so, if the image is larger, then it becomes the parent, and I suppose if they are the same size, then the older picture stays to give credit to it's uploader?

yes, and if an image is indeed a dupe, Flag it and link it and I'll take care of it.

Okay then, so the official tag is "dupe".