If you wipe the exif, they will have other excuses to reject - their infamous "artifacts" or "overprocessed" reason for example. Those just make me shrug. It's either extremely unqualified people who are not able to tell what artifacts are if they bit them from behind, or people driven by conflict of interest since they have photos of similar subjects in their portfolios. Both cases are indications of amazingly unprofessional environment. I was asking agency owners years ago - don't you think it's a conflict of interest to allow reviewers to have their own portfolios on the site? The answer was always - nah, it's fine...
I had a couple of submissions recently returned for the need of extra model release (a small part of the back of they guys head was visible), so we went ahead and added the release, now they rejected those images for "use of direct flash". Needless to say, no direct flash was used, not even close!
I am sure there are many talented and knowledgeable people with good work ethics working as reviewers on Istock, but there are also way too many unprofessional people in my opinion.