I was putting a bounty on a question for the first time, and the text window started bugging out.
As you can see, some of the prompt is cut off on the left-hand side (the "E" in "Enter", the "Ar" in "Are"). More frustratingly, my text was altered in the middle of typing. What I actually typed began "This is a great question" and ended "based on", but the substitutions
The change seemed to be associated with the linewrap in the text box. Also, the final version came out fine, it was just my display that was wrong at the time.
For what it's worth, this occurred running Firefox 22.0 on a Windows machine.