Hmm. When working on
long, long postings, I use an external editor. Then, I copy into the browser, and press "Preview". If I like what I see, I paste it in again, and hit "Submit". If I don't like what I see, I go back to the external editor and try again (I normally post from my Mac, so use TextEdit or TextWrangler. On PC's I make do with Notepad, but sometimes I load up some text editor.)
The key is not to edit in this blank line eating environment; it really messes up readability of the posts.