Ecumenism, leaping ahead of where we might be in relating to one another as separated sisters and brothers, is a concern:
[8.] It is therefore to be noted with great sadness that “ecumenical initiatives which are well-intentioned, nevertheless indulge at times in Eucharistic practices contrary to the discipline by which the Church expresses her faith”. Yet the Eucharist “is too great a gift to tolerate ambiguity or depreciation”. It is therefore necessary that some things be corrected or more clearly delineated so that in this respect as well “the Eucharist will continue to shine forth in all its radiant mystery”.
Intercommunion might be one such practice. Roman clergy participating in sacramental celebrations outside of the Roman Rite would be another. And yet, one gets the idea that Jesus is rather strong enough to survive good, but misplaced intentions. RS 167 will treat this subject.