The reviewer is a skilled experimenter, whom I enlisted to check my understanding of the physical processes. (By the way, this person knew what I was saying, just didn't like the way I said it. For our internal reviews, we tend to get pretty picky.)
It's definitely not for a general audience-- there'll probably be five people in the world who can use the paper directly (once the results are embedded in software, there'll probably be several hundred who will use it).
How can anybody with a grade school level education not understand that? Are you sure the reviewer couldn't turn it into a sentence? Or perhaps the reviewer didn't feel that was the proper formatting for a sentence? I'm not sure how else you would include equations in a sentence, but if my reviewer didn't understant grade school level mathematics I'd be horrified that this person was in a position to be reviewing anything at all.
When a sentence had an identifiable "other" verb-- for example "Then substituting gives x = y/2"-- everything was fine.
The reviewer actually made some incredible suggestions for restructuring the paper to bring out the important points. I'd hate for people to come away from my original comment thinking the reviewer is anything other than a very bright person who was pushing me to make the paper as clear as possible.