From using it myself, and in discussions with friends who both travel and host, "I'm sorry, it's not available those dates" is the polite way of saying, "I looked at your profile and don't want you in my home."
Somebody just submitted one hell of a job application. If I was AirBnB, I'd take note and action.
We do #2 - #5 but could get a lot better on #3.
It's a challenging problem to solve. I just offered a few quick suggestions from an outside perspective.
I just hope, as an active customer, that AirBnB will invest resources at some point to minimize this problem.
It's very frustrating.
Yea, we're actively working on tackling it from all angles.