Why do some churches eat leavened bread and wine for the Lord's Supper? Why is it that many denominations partake of leavened bread and wine during the Lord's Supper when the bread and wine of the original Supper was unleavened? The Passover coincides with the start of the Feast of Unleavened Bread.
Theologically, Episcopalians liken the leaven to the power of the Holy Spirit giving lift and rise to the loaf. As an Episcopalian myself, however, my pragmatic analysis is that this is primarily because they like the taste better (silly 'Episcopalians).  I, too, however dislike the symbolism, because in my mind, leaven is associated with sin.