This occurred only when I installed 2.3
Very simply, the word wrapping "turns off" after roughly 20-30 lines of text. Upon posting, the offending line of text indeed extends far outside the normal post margin/bounds.
I've done a work-around by cutting and pasting all text into an external .txt Notepad file and then pasting it back in.
Again, I've never once had this issue previous to 2.3
Using latest Opera and WinXp, BTW.