Good thing I searched for edit first before attempting to post the same thing.
I find it quite annoying myself that it is impossible to edit the original post.
If you're going to allow editting of replies, why not the post itself?
For me, I know this is pathetic, but when I'm on Lynx, I only have 10 lines or so to type a post, therefor using <code> and <pre> tags become impossible to use.

What I like to do when I think of something to ask that requires me to add code, I'll post it with Lynx as "I'll add the code later".
Now if I could edit the original post, adding a reply to my own post would be unneccesary and save "Valuable Resources", as I've heard said before would not be wasted.

As for the preview button... If you've noticed, there is a little problem with the preview button.
If you include any special characters, such as &lt; and &gt;, hitting preview does this:
It goes to the preview page sure, but now look at the textarea: the special characters disappear and are replaced with that character it represents!

This is VERY bothersome, as you can imagine!