@Kelly149
We're also very picky about who books. It's an essential part of hosting, if you seek to avoid bad situations.
I'd say we've done a pretty good job of weeding out the undesirable guests, but you occasionally get them, despite your efforts to avoid it. Unfortunately, your ratings can take a hit or you can lose superhost status simply due to a guest whim, having nothing to do with the quality of the accommodation.
We've just had one such guest, I strongly suspect is a subscriber to one of those "get cheap or free Airbnb holidays" blogs. This one was looking for refund opportunities from the minute they arrived, and attempted several times, though largely unsuccessfully.
In this case, I have to give Airbnb some credit, because despite the guest demanding a 50% (~1500€) refund for a fabricated/grossly exaggerated grievance, they only gave him 240€.
Nonetheless, I'm expecting a bad review, one that will affect my ratings for the foreseeable future, all because one dubious guest was seeking a cheap or free holiday.
Well, that's just the nature of hosting. Like you, prevention is always the best cure, but there's always one that will make it through the gauntlet.
Happy hosting!