There's this one thing about editing posts or comments that is missing from a standard installation of eZ Publish in my opinion. That is the store button (save and continue editing).
One thing is that maybe it could be possible/useful to actually let users store their texts and come back to the editing and publishing later. That would of course be a little bit more complex as we would have to provide the user with access to her/his drafts.
Another reason is that storing without publishing has this miraculous capability of fixing or "stabling" the document structure created with the OE. The preview "side effect" of this would be very welcome as well. I do realize that the introduction of JS/ajax replies made things a little bit more complicated, but not impossible, right?
Just maybe a thing to think about.