I believe it's ok to discuss the theories of Elenin on Five Doves since the people here are already watching and waiting for HIS soon return. I do NOT think it's a good idea to use Elenin as a scare tactic to try to win people over to the Kingdom. That isn't likely to work, and like you said, will simply cause a weakening of credibility.
Many people in our Churches are sound asleep and totally oblivious to how close we are to the end, so perhaps using the speculation of Elenin as an ice breaker to get into the topic of end time events would be helpful, as long as we aren't trying to push one end of the spectrum or the other.
Christ is coming back very soon and we need to be ready and get as many other people ready as possible.
I love showing the nearness of the hour to the skeptic, and how all these things were prophecied thousands of years ago. It's a great witnessing tool, however, I prefer to use information that can be verified from multiple sources. I see nothing wrong with debating Elenin in a public forum such as this, just not as a witnessing tool, since all of the information is ambiguous at best. God Bless, and Maranatha