[davidschaengold]

Once a conversation is published, you can no longer choose not to accept your counterparty's messages. However, if you choose not to respond to further messages in that conversation, your counterparty's additional messages will be considered "post-scripts," which do not cause a conversation to rise to the top of the Explore page. The effect is that, while no user can claim the last word from a counterparty, you can make it unlikely for a conversation to be seen by simply allowing the other user to have the last word.