Unless the reviewer has a forum account, and therefore access to our PM system, no. We don't permit replies to reviews on the review board itself, and the only other option I can suggest, if your reader doesn't want to follow a url to the forums, would be to place a very brief reply to that review at the end of the next chapter of your story.
I stress brief here, because we have a limit on the length of author's note content allowed in a chapter, and such notes can't total more than 600 words. We do check that, and we do warn a member if heir author's notes exceed the limit. I would further suggest any note contain the url to the forum review reply thread for your story. Your readers do not need to be forum members to read or reply on the thread you make, and it's much easier to have a lively conversation here rather than in the archive itself.