I don't use this module and can't find it somewhere. In prestashop store there are a lot of such modules.
Why it's no more working with 1.3? Not sure. I could imagine, that it's related to customer merge function. As you describe the problem, it seems that the customer is not deleted at all.
From my own experience, I fear the deletion of customer accounts. It can bring up a lot of issues with external modules and maybe even with the core. I prefer to hold the customer object, but randomize it totally. What is the opinion of other coders like @datakick, @zen, @cienislaw, @musicmaster, @yaniv14