I can't describe how many times I've entered a comment, submitted, and had the submission fail for some unknown reason. This wouldn't be a big deal, except it destroys the comment box, and everything in it, so everything I've typed is gone.
It's gotten to the point that I try to remember to do a copy of the box before I submit, but when I've typed a lengthy comment, it can be very frustrating to have it disappear completely, destroyed by a cat saying "it's not your fault". Small consolation.
Would it be possible to not erase the comments field until the comment has successfully been submitted...an error report would just be appended into the page, rather than replacing the comment box.
Not sure about the feasibility/ease of this, or how many people it would help...but it drives me batty.