We excommunicated people over how they sang a hymn, one entirely theologically appropriate in its context. Somehow I don't think this reflects well on us :-).Here
is a Catholic commentary on the Quinisext Council or Council of Trullo. It must be noted that the Latin view is that the Council of Trullo is not ecumenical and that the Greeks themselves recognized the need for Papal (Roman) ratification of a council for ecumenicity. From a Roman view, about half of the 102 canons were against the Latin church.
Regardless of the ecumenicity of the Council of Trullo's canons, let's see what this Catholic commentator said on Canon 81.
The council forbids the addition of the phrase "Who was crucified for us, have mercy on us," to the Trisagion hymn. The penalties of deposition and excommunication apply.
Though this phrase can be given an orthodox interpretation, it was abused by heretics to suggest a single theandric nature in Christ, since it says the one who is crucified (human) is the one who has mercy (divine). Peter Fullo added this phrase in 478 with the intent of implying that the true God died on the Cross. Those who insist on retaining this unnecessary phrase may justly be suspected of Monophysitism, hence the penalty of excommunication."
The commentator's phrase that is most alarming is "implying that the true God died on the Cross." This apparently Nestorian comment corroborates Fr Peter's observations against those who reject the Trisagion additions are rejecting fundamental anti-Nestorian Cyrillian theology.
Not only does this Oriental Orthodox theologically appropriate Trisagion hymn reflect badly on the Council of Trullo and Eastern Orthodoxy, it also reflects an anti-Oriental Orthodox prejudice that is dangerously close to Nestorianism.
Now regarding the Oriental tradition that Joseph of Arimathea and Nicodemus sang the Trisagion, commonly taught among the Coptic Church, does not have any manuscript evidence until the 8th/9th century with Bar Siba. And thought this might seem too late, it is contemporary to the earliest Chalcedonian history by John of Damascus in the 8th century and much earlier than the 14th century Chalcedonian historians like Necephorus Callistus who give the origin of the Trisagion to a miracle during the episcopacy of Proclus between 434 and 436 AD. This speaks only of written manuscript evidence.
It is quite probable that an oral tradition of the Trisagion origin to Joseph and Nicodemus is much earlier.