I'm afraid you're going to need to spell it out to me. What are the opportunities for abuse here that aren't already present in the form of private WhatsApp groups or shared Google Docs with lists of accounts and abusive notes about them?
I'm not saying there aren't any, but my imagination hasn't been able to come up with anything more than "it makes it slightly more convenient for co-ordinated harrassers to remember who they were planning on harrassing".