Yes, it's happened a handful of times. Also, sometimes my comments get corrupted into weird code.

I've gotten to the point where I Ctrl + A, Ctrl+X, then Crtl+Z before posting. That way I have my post on my clipboard in case the post vanishes or the comment corrupts. (I use Ctrl+X instead of Ctrl+C because when you use X, the text vanishes and you have visual confirmation that it's on your clipboard.)