>> "I was just idly wondering today whether I could easily delete all my posts from high school (full of angst about calculus and bus rides)."
Although I agree with your feature request why does it matter to you that that stuff is there? I enjoy going back through my timeline (maybe once a year or so) and seeing old things. There may be a few things that make me cringe but there's nothing so embarrassing that it would have any effect on me currently should anyone else see it.
Probably just me but that sounds crazy (very possible you use it normally while I don't). I've deleted then returned to FB many times. Even when I'm not deleting my account, I always clean out my past posts, sometimes a few days later (after posting them) while other times I'll wait a few weeks. If I add a new profile pic, I usually delete the old one. Also, I talk to people via PM.
Although I agree with your feature request why does it matter to you that that stuff is there? I enjoy going back through my timeline (maybe once a year or so) and seeing old things. There may be a few things that make me cringe but there's nothing so embarrassing that it would have any effect on me currently should anyone else see it.