I am of the same opinion you can never judge how a person lives.Ive had the same with My Deposits. The tenant did not leave my property clean and the cat scratched an area of the carpet pile. They said the photos were not clear. I did retain some of the deposit allowed by MD however not to the level of what the value of the catpet was and cost of cleaning. I have also used an agent to carry out an inventory since then and the tenant in question left the property in a reasonable state of repair with very little to do. Maybe the inventory made her realise she would lose money but who knows. Its all down to pure luck if you ask me and maybe instinct as well.
Good Luck
Julie