I suppose there is an element of trust, the moment you engage in what is basically the start of an employment. Just like you don't bad-mouth a former employer,

I suppose there is an element of trust, the moment you engage in what is basically the start of an employment. Just like you don't bad-mouth a former employer, you don't do so with an almost-former-employer. Try to turn it on its head - Wouldn't it clearly be out of line if a potential employer discussed a candidate openly? On a scale of misbehaviors, this is probably far on the "good" end, but still. Who should gain from this post? If Airbnb, why not mail them directly? If he is "warning" potential hires, aren't he in effect hurting Airbnb? If he wanted to discuss hiring practises in general, why not anonymise them?