A global conversation is a conversation that takes place on several web site simultaneously. You can tell that you are looking at a global conversation because it says "Global conversation - learn more" underneath the title of the conversation.
When you post to a global conversation, such as "mandolins", the post not only shows up on the web site where you posted it, but it also shows up on any site that chooses to embed the conversation, now or in the future.
Site owners can embed a conversation by clicking the "Embed this" link at the bottom of the conversation and copying and pasting the code into their site.
Deleting a post. You can delete the a post you have created at any site that hosts the conversation. The deletion will be instantly reflected everywhere.
Objectionable posts. Next to each post is a flag that marks a post as objectionable. If enough people who are viewing a post click the flag, the post will be automatically removed.
Site owner options. An individual site owner who hosts a global conversation can only choose to either include the conversation in it's entirety, or remove it. As a site owner there are additional alternatives: