No idea since Diabol uses cmp to create dats just as the other guys.
In the C64 sets i bet there was something like ' instead of "\", maybe Duncan can explain better how that happened (it can also be related with some error trying to replace / script something and escaping ' with \'?)
Thanks for pointing them out!
edit: noticed that Cassiel already reported that
here and in his case they are actually "`" instead of "\". Strange, eh?