Can there please be a notification of such limit? Whilst we are typing the response would be best, but it could be applied the same way the minimum character limit warning is applied.
You're actually complaining that your enormous post in the formatting sandbox was truncated?
I'd be more amenable to this request if someone actually wrote a real post that long, and had a legitimate complaint that it got truncated.
edit: we really should be warning users when they enter a novella body text that's too long, rather than just truncating silently. I added a saner check for this through the standard question form validation.
If you're writing anything 40,000 characters long (about equal to 7K English words) in one piece for any Internet forum, you're doing it wrong. Srsly.