I don't see importing really working all that well. Like the other commentor said, without context (the original post and other comments) your own messages are pretty much useless. And while not impossible, I don't really see how you would import an entire thread with other people's comments, because they're different users. Letting just anyone upload an entire thread including other users comments would open up an instance to A LOT of spam.
Shred-it bro
Love this video, Shred it! Broooo
In all seriousness though I probably won't be deleting my stuff either. Less than a month ago someone replied to a message of mine that was years old and they said they found it when googling. I don't want to ruin someone's day when they try to find something to answer their questions.