Is there a bug when editing a post?
To reproduce follow these steps.
a) Reply to post
b) Edit to correct a typo maybe
d) Edit again as you spotted another typo - the editable text then does not load the latest correction.
I am using IE 11. Not sure if it happens all the time but I have noticed it a few times. The only way to be sure would be to test more thoroughly but that would mean a thread with lots of test posts which I'm sure you don't want.