You are correct in sensing that there is more unity than difference in the way Catholics and Lutherans understand and celebrate communion. In fact, since the Second Vatican Council there has been a “coming together” of these different Christian Churches with respect to communion. The Catholic Eucharist (Mass) is now celebrated in the language of the local community rather than in Latin. The communal celebration of the Mass is much preferred to the private celebration by a priest that was common before Vatican II. And Catholics have restored the ancient practice of communion under the forms of both bread and wine.
In dialogues between Lutheran and Catholic theologians in 1968, Lutherans agreed that the celebration of the Eucharist involves a sacrifice of praise and self-offering that unites the believer with the sacrifice of Christ. At the same time, Catholics joined Lutherans in affirming that the sacrifice of the cross was a unique, one-time event that is not “repeated” in the celebration of the Eucharist. Both Lutherans and Catholics affirmed that in the Eucharist Christ is “present wholly and entirely, in his body and blood, under the signs of bread and wine.” This “presence” of Christ in the Eucharist is more than a commemoration; it is an “effective sign” that “communicates what it promises” (“Building Unity,” Ecumenical Series IV, editors Burges and Gros: Paulist Press, 1989).
There remain some differences between Catholics and Lutherans with respect to communion. Some are matters of vocabulary. Each church forms a kind of culture with its own vocabulary and terminology. For example, Lutherans will refer to communion as “The Lord’s Supper” while Catholics prefer “Eucharist” or “Mass.” A shared vocabulary helps a group feel comfortable and at home. Sometimes differences in vocabulary make it seem that there are differences in meaning where none actually exist. It’s very important to learn and attempt to understand the vocabulary of another church in order to have a meaningful conversation.
True differences in belief and practice also remain. While both Lutherans and Catholics will bring communion from the church to members of the community who are sick, Catholics maintain the practice of reserving the communion bread in the tabernacle, which becomes a place of prayer and devotion. Lutherans do not hold the same belief that the presence of Christ continues in the bread and wine after the time and place of the celebration of the Eucharist.
Lutherans would also question the Catholic practice of offering Mass for the intentions of those who have died. While Lutherans believe in the value of offering prayers for those who have died, they would have reservations regarding Catholic belief that the Eucharist is effective as an “atoning sacrifice” for those who have died.
Catholics hold to the term “transubstantiation” to describe the reality of Christ’s presence in the Eucharist. They borrow terms from the philosophy of Aristotle to express the belief that during the Eucharist the substance of bread and wine is changed into the substance of the body and blood of Christ, while the accidents of bread and wine (what they look, feel and taste like) remain the same as they were before. Lutherans prefer to avoid the term transubstantiation and use other terms to describe their belief in the full reality of Christ’s presence.
Since I am not Lutheran, I may not have done full justice to the Lutheran position on the Eucharist, and would welcome any corrections from those who know more. However, I feel certain that there is much more agreement between Catholics and Lutherans on this matter than we often realize. I thank you for your most interesting question and hope this has helped to provide an answer.