This topic has been extensively discussed on this forum during the last few years, but I don't see much discussion on it lately. So this is an invitation to renew the debate on the subject. It seems to me that there are still open questions and I haven't seen a good analysis of it. I personally think that Anton Zeilinger's explanation on his paper "Experiment and the foundations of quantum physics" does not answer all the questions and some of his statements may not be correct. For those new to the topic, an introduction can be found in: www.paulfriedlander.com/text/timetravel/experiment.htm A common point of disagreement is if the coincidence counter plays any role besides eliminating photons that don't have an entangled partner. Some say that without the coincidence counter you could never see interference in principle even if all the "noise" was eliminated. I haven't seen a good explanation as to why this would be true. John Cramer at the University of Washington had claimed he would run an experiment equivalent to Dopfer's but without a coincidence counter, which would enable sending messages "back in time". I don't think we have had any news about his experiment lately.