Yes, in Catholicism a Protestant marriage is valid, so a couple wanting to convert would not have to have their marriage validated. However, if a couple just has a civil marriage from their local courthouse it's as if they are not married at all. Again, as far as receiving Communion goes in Orthodoxy, is it not the same?
Going back to Porter's Simpsons post, I'm not sure what issue you think I'm avoiding. If Catholic teaching can't change, and we've been assured by individuals here that it cannot, then what is now happening is that people who are in an objective state of mortal sin (having sexual relations outside of a sacramental marriage) are being allowed, if not outright encouraged, to commune which, when done in a state of mortal sin, is itself a mortal sin. And to die in mortal sin sends one to Hell. It seems to me that if the preceding is still true, rather than helping these individuals to "stop hitting themselves" the growing number of hierarchs permitting this is actually doing great harm to them and their souls. Again, if Catholicism is true and these people want to remain Catholic, they do have a choice - don't remarry or if you do remain continent. At least that was the case, now there's just a growing chaos post-Amoris and they can do whatever they want apparently. Personally, I'd invite these people to consider Orthodoxy, that's also a choice...