We should particularly pray on this feast day for Pope Benedict, that he may continue to fulfil his office as universal Pastor with vigour and faithfulness.
Be it for the Holy Father or the diocesan Bishop, the Chair represents both governance (in the pastoral sense as much as the juridical sense) and teaching office. Cardinal Ratzinger, writing in "The Spirit of the Liturgy", likens the chair of the Bishop in the Christian cathedral to the chair of Moses in the Jewish Synagogue. This is where the people gather to recieve teaching, not the personal views of the Bishop or Rabbi, but the word of God revealed, respectively, in the Gospels and the Torah.
What can this tell us about the priest's chair in a parish church? By analogy, we would expect it to represent the office of the parish priest in respect of his parishioners. If the parish priest is not the celebrant at a particular function, it could represent at a lower level of analogy the general priestly office of governance and teaching. The meaning of the chair is therefore one of pastoral/juridical governance and teaching.
However, beginning with the instruction Inter Oecumenici on the implementation of the Conciliar Constitution Sacrosanctum Concilium on the Sacred Liturgy, and continuing through to the most recent General Instruction on the Roman Missal, the role of the Chair is expressed in terms of "presiding":
"The priest celebrant's chair ought to stand as a symbol of his function of presiding over the assembly and of directing prayer" [GIRM 2000 n.310 -unofficial translation].
This language seems to focus on the activity of the priest celebrant during the Liturgy, and defines the meaning of the chair in terms of that activity. You would almost expect that, when no Liturgical celebration is taking place, and therefore no actual presiding is taking place, the chair should be removed from the Church. The activity of the priest celebrant during the Liturgy derives from an office that is manifested in the Liturgy, but not limited to it. The pastoral/juridical office of the priest finds a particularly vivid manifestation in Liturgical celebrations, particularly during the homily at Mass, and this is where the dignity of the chair gains a relation to the activity of the priest during the Liturgy. But the chair is also a sign of an office that extends beyond the Liturgy.
This all has two practical consequences. The first of these is the question of how priests view their activity during the celebration of the Liturgy. If they are "presiding" they will feel able to ad lib and perform, rather like a chair person of a committee. If they are "exercising their priestly office" they will respect the structure of the Liturgy as expressed in the rubrics and provided texts. The second is a question of the direction in which the chair faces in the design of the Church. Again, if the priest celebrant is "presiding" it becomes a matter of importance that the chair faces towards the people. If the celebrant is "exercising a priestly office" it may well still be desirable that the chair faces towards the people, but it does not become of the essence. A diagonal or sideways orientation of the chair (in which it faces towards, say, the altar) becomes acceptable.
It is true that, read within a hermeneutic of continuity, the language of "presiding" can be readily assimilated to that of an office of pastoral/juridical governance and teaching. However, such a reading of it seems to be rare.
[And, being completely mischievous, how often is it in fact the Master of Ceremonies who "presides" in the sense of "directing" the activity of the celebration? The bishop's visitation can be the one chance the MC has to tell a bishop what to do, and get away with it!]