For all the sellers who can't be bothered with seeing the "is it available" messages, you need a better understanding of how the system you are using to sell works. If a potential buyer looks at an ad several times, FACEBOOK will send that message. It's automatic. Doesn't happen every time, but Facebook does this to generate traffic. So stop accusing buyers of being ignorant and obnoxious (which they actually are for other reasons) and become less ignorant of the platform yourself.
And, no, of course Facebook doesn't admit to doing this, but you can test it. Click on 10 or so different ads, 7-8 times each, and eventually you will get a "yes it is available" response.