Sir, - What is the "worst case scenario" from either standpoint?
If a Catholic eats the Protestant Eucharist, as far as the Catholic "eucharo-phagist" (eater-of-good-grace) is concerned, (s)he has eaten ordinary bread - powerfully symbolic bread, but harmless, demystified bread, nonetheless. The Protestant, in all her/his generosity of spirit, is happy about the Catholic doing this. No problem to either "side", one would hope.
If a Protestant eats the Catholic Eucharist, as far as the Protestant eucharisto-phagist is concerned, (s)he has eaten a powerfully symbolic piece of bread. As far as the Catholic is concerned, the Protestant has eaten the flesh of Christ. Atavistic taboos aside, this could only be a good thing. I am not being provocative when I say that I presume Christ himself would not be choosy about the recipient. He used to walk around and touch people, we are told. Caringly touch them, believers or not - me, therefore, included. - Yours, etc.,
John Kieran, Westfields, Blackrock, Co Dublin.