I've deleted no reviews since I first began posting fiction online in 2008 simply because I was feeling hurt by what the reviewer said. Sadly, I lost all my reviews on FFN when I removed my work there due to the rampant plagiarism and lack of moderation on that site.
Having said that, I will admit to having deleted a few non-reviews. Two were responses to warnings I'd left as a moderator here, and the authors posted to my review board rather than emailing. I replied via email, but deleted the non-reviews. The only other non-review I deleted was posted on the latest of a series of prompt response one-shots I had done, and the reviewer was posting in retaliation for my having warned a friend of hers. It was obvious from the review that she had simply gone to the first subdomain where I had something published, and grabbed the story at the top of the list, which, as anyone with sense knows, would not have been the first thing I'd published, but the most recent. It was not a serious review, and although I have retained a screenshot, I did not dignify that idiocy with a response, nor did I feel obligated to keep it, typos and all, on my review board.
For the most part, I try to respond to all my reviews, and my review threads are right on my profile. I love a good discussion, and I love good concrit even more.