I understand they're your posts and it's your choice, but my gut reaction is still 'OH GOD WHY WOULD YOU DO THAT D:'
Understand where I'm coming from here -- you still have evidence of your start in the fandom. As far as MX cares, I pretty much never existed. The first forums are gone. MR UK is gone. The fanfiction.net forums are pretty much the only place left where I exist in MR fandom D: (well, besides here).
Sorry, but I second what Nathan said for different reasons.
If you delete them, it looks like you're denying what happened.
1) It's destroying memories. The mods do enough of that anyway.
2) If somebody calls you out on it, the conversation is dead, and it looks like you're trying to hide something.
It's your posts, your decision. But I still hold that personally, nobody should delete posts.
I got into an argument with this girl one time. We were friendly later on, but she said she was going to delete her posts from the argument, to 'forget' it or whatever. Immediately, Lamp, Ranting and I yelled at her not to do that. You just.... don't delete them. In my opinion. Not that it matters.
That fic is epic bad XD "Voldemort's Daughter" is worse, though -- either the document got massacred, or I couldn't find the spacebar blind and took heavy drugs before chapter 3.