Report from the refereeing trenches

I am currently refereeing the revised version of a paper I had previously refereed. (Actually, I have been doing a number of these lately, but I have a specific one in mind.) One of my comments on the original version of the paper was that there were severe grammatical problems (and typos) that needed to be fixed. In their response to this point in the cover letter, the authors wrote:

"We have checked spelling and did our best to improve the grammatic."

Dude!