To eliminate at least one possible source for the problems you’ve been seeing, I’ve rewritten the live comment preview. It’s no longer a plug-in performing event-driven surgery upon the page after it’s loaded; instead, it’s coded directly into the comment form. Is it any better now? any worse?
(As the plugin code was written, it was trying to install hooks on every Daily Pundit page — including the Admin pages — rather than confining its attention only to the single-post pages, so you may see improvement across the board from this.)
Everyone else: Let me know if you see any problems with the live comment preview.