From Bonnie Honig in Antigone, Interrupted,
I am one of those people who finishes other people’s sentences. Some people see such interruption as impolite and resent the institution. Others appreciate it and see it as a part of a kind of conversational co-stewardship. You can tell pretty quickly which are which. With those who resent the intrusion, I hold back and try not to let them hear my foot tapping as I wait for them to finish making their point in their own way.
Although often offered in the spirit of mutuality, interruption can be a sign of power. In the parental injunction “please do not interrupt me; let me finish my sentence” which I have had occasion to utter from time to time, I hear the power I disavow elsewhere. And to my kids’ response “but you interrupt us all the time!” I can only laugh and shut up. (I think everyone should have a kid in their life — you don’t have to have one, just have one in your life — so you too can learn to laugh and shut up.)
As a social practice, then, interruption postulates both equality, as when two people interrupt each other to knit together a conversation in tandem, and inequality, as when one party must yield the floor, as it were, to the other (p. 13).