I think that if somehow (after a few drinks, or whatever) a discussion of DD comes up, it might be interesting to talk about it with some other people in real life (IRL, I guess? I don't speak "internet" very well). But, like RT said, if the discussion goes somewhere you don't want it to, then I think it's fine to say so. Just lightheartedly say, "Whoa, I don't want to go there!" and laugh it off.
Topper, as for you being uncomfortable with your guests' spanking-- other than communicating with them beforehand, I'm not sure what to tell you about that. There is a point where TTWD crosses over into sex (TTWD is, to a certain extent, a play-out of fantasy for me, even though, to me, it's very very real, if that makes sense), so I can see how you would be uncomfortable with the guest bottom coming downstairs with red eyes or something. That could, as Dan Savage has said before (anyone else read his column "Savage Love"?), could feel like you are an unwilling participant in their "sex game*," whatever it is to them. I would think, though, that if they didn't know you guys did TTWD, or you'd never talked about it, that they would be discreet-- take care of spankings and punishment at night at bedtime, and only discuss it with you after it had been established that that discussion was okay. That's what I would do, and what I plan on doing when Daddy and I travel.
If it's any consolation, I'm pretty nervous about how "out" Daddy and I will be when we travel this summer, and having never talked about TTWD in real life with anyone else but Daddy, I am pretty nervous about those conversations and meeting these people who know about TTWD together, but who haven't met me personally.
*I know that to me, and to most (all?) of us, TTWD is not a sex game. But for many of us, there is a sexual element to TTWD, so I am just saying that I can see how one would be uncomfortable watching others do TTWD-- what we do is very intimate and close and personal, and hard to share with others until those boundaries are set and everyone is comfortable.