Sounds like it’s done by address, so the slumlord’s name isn’t necessary. Seems like a great idea.

Exactly this - reviews of addresses and businesses, not of people!

It's not libellous to publish a factual statement (ie the landlord didn't return my deposit).

No it most certainly is not - I look forward to seeing your factual statements on the platform :) We'll be filtering out names so that reviews are attached to addresses, with a background effort on tying together problematic landlords and their property portfolios with some help from the housing unions.