From a technical perspective, it is certainly possible to delete all of a member's posts. From a policy perspective, it is not something we currently do.

From the FAQs:

Who owns my post?

For the sake of simplicity, we'd say that we own anything posted on FlyerTalk. Our reasoning is that we have the power to edit or delete any post if we, representing the community, find it provides more harm than value to FlyerTalk. Also, if a member decides they no longer want to participate in the community, we would find it difficult to go into the database and delete each post an individual had made. Excerpts from posts to FlyerTalk may appear in InsideFlyer magazines, books, or other materials.

Of course, policy decisions are always up for revision, but at this time the short answer to the original question is, we do not remove posts upon a member's request.

I understand this probably isn't the answer you were hoping for birdstrike, but I hope it helps clarify the current policy.