The thing is, I don't see anything in Rdunbar's post to suggest that he had already ceased to be Catholic.
elijahmaria has already explained that she believes that "there's really no point in talking to" me, but with regard to the rest of the posters on this thread I can't tell whether you agree with what I said, or whether you disagree but haven't gotten around to arguing against it ...
Maybe he hasn't "officially" ceased being Catholic, in the sense of not yet having converted/translated to Orthodoxy, but if he or anyone else, as Papist wrote, can no longer profess the (non-Orthodox) Catholic faith as defined by the Catholic Church then whether or not they have "officially" converted, he/they are no longer really and fully Catholic. And given that Rdunbar *apparently* can no longer profess the Catholic faith, perhaps he would be better off in Orthodoxy. I, for one, would not begrudge him that at all. It saddens me some, but he must do what he must do.
I'm not sure if the above constitutes agreement or disagreement with you, but perhaps it isn't a black and white as that.
That sort of raises the question of those Catholics who no longer practice their faith or any other. You know, the so-called "lapsed" Catholics. Are they still "Catholic" or not? Same question can, of course, be asked of "lapsed" Orthodox. I reckon that by virtue of their baptism, and unless they had somehow actively renounced the faith, "officially" they would be, but in their hearts and to be counted as "true believers" in the best possible sense of the term, probably not.