If you want do complaint for the theft and resale of your images to Shutterstock,
https://shutterstock.my.site.com/support/s/dmcacomplaint?language=en_US
you have to tick and agree this in the form: 

"I understand that Shutterstock may provide the affected user with a full copy of this complaint, including my full name, email, street address, and any other information included in my report, and may provide a version to third parties, if requested."

"Note that any abuse of this form may result in the termination of your customer or contributor account."
But, thieves only risk deleting of the files concerned... "you may request that the content be removed from Shutterstock"

Let's be reassured, Shutterstock is very respectful of thieves

lol, yes, funny + messed up. how about shutterstock gives the full details of the thief's account? ah, but then thieves would probably start filing fake dmca reports to steal  that info too...

simple solution:
a) don't allow accounts from east india/nigeria/etc - because most of the 'stolen' content originates from there. it's an accurate stereotype, because those tend to be the 'business models'.
b) if it has an east indian name, don't allow the account to be opened, again --^ see above. OR - require extra proof that the assets are indeed there's - OR - do a little extra checking before allowing such an account to be opened up.

All of the image thieves i see are from India/Pakistan/Sri-Lanka.
The various FB groups have multiple posts from these every single day.

Shutterstock really doesn't give a toss about stolen content though.  Its own engine SHOWS the identical stolen or rotated images from 4-5 accounts under the current one yet it's not checked at all during upload or "review".
Non-sensical or garbage AI descriptions aren't checked.  There's clearly no human at all involved in the submission process now.

I suspect to SS a sale is a sale no matter what account.  The chances of any real legal fallout from allowing it are absolutely miniscule and simply not worth worrying about, so they just let it go.

DMCA was and has been weaponised by malicious actors against legitimate contributors on there as well, again due to the way their procedures, lack of verification and non-existent support works.