Companies regularly do searches for blog posts, forum posts, and other things online that mention them. Not sure why finding and commenting on yours would be a violation of their privacy policy?
Their policy states that buyers and sellers are not supposed to try to access each others' information and that information such as e-mail addresses, names, etc. will remain confidential. By commenting on a purchaser's blog they violated the spirit of that policy, as well as the agreement that if you 'uncheck' the box allowing them to contact you, for issues not directly related to specific orders (the post did not contain my order number, it asked that I respond with my order number, therefore it was a general "we saw a complaint now we must stop it" post rather than a "this person has a complaint and we should do something about it" post) they will refrain from contacting you. To remain within ethical and privacy boundaries that they set, they need to give you every opportunity to contact them with your concerns, but to avoid seeking you out and contacting you.
I suggested that instead of that, they offer a satisfaction survey at the end of each transaction.