::I don't see exactly what is the exact contradiction you claim, the issue is still needing further details to be solved. The difference in the heat of formation of water and semi-deuterated water is inconclusive about the differences heat of atomization and of formation of different isotopes as it is clear that transition from one isotope to another requires a nuclear reaction of at least one neutron capture or beta decay such as in the tritiation of heavy water moderator due to neutron flux or similarly to the deuteration of light water. It is clear that some paradoxical/anomalous situation is involved requiring further investigation. Of course statements should be backed by sources in order to be a verified information in wikiarticles. 
 ::Does the source you mention contain the heat of atomization of deuterium, tritium and hydrogen deuteride to be compared with that of hydrogen to see where the anomaly comes from? It is clear that there must be a difference of some sort between isotopes, the exact nature and numerical value has to be determined. So about the wording I'd leave out the statement about neutron capture difference but clearly the difference between isotopes should be mentioned with the specification that is of an unspecified nature.