I just did a transcription where the interviewee says: Either you know or you don't know. If you know, you know. You know? Haha. I just thought it was hilarious. Can't wait to see how it gets edited. I think the last "You know?" doesn't fit the style guide, but I just had to leave it in.
I think I'd leave it in because it SEEMS as if the speaker is making a joke. Without the audio, I can't say for sure, but either you know or you don't know. You know?
Ha! I love that, too. I agree: leave that last one in. Although it could be said to be redundant according to by-the-book style, the fact that the speaker said it adds a lot of context. Taking it out would have caused that to be lost. And that's one of the tricky things about transcription: it's just as important to preserve the feel of what's said as anything else.