what is this broken metal strap(?) Grounding strip? It's super thin and I can't figure out it's purpose. Is it important enough to replace? Thanks in advance!What is this?

 

certainly appears to be a ground strap. That's the boot hinge? Is there a strap on the other hinge? If so I'd not worry about it. If no I'd probably solder a small piece of wire between the two chunks to restore the function.

 

Mine is broken as well.

 

if all your back end lights are working I'd not worry, but monitor ....