Found this very useful. Bill Kee from the Official Gmail Blog had this tip to share. I can think of more than one occasion where this would have been used me and the missus.
I use the “m” shortcut key to mute the conversation and spare my inbox. As new messages are added to the same conversation, they bypass my inbox. If someone puts my email address directly on the To: or cc: line, the conversation immediately re-appears; otherwise, irrelevant messages sent to the mailing list are archived. That way I can refer back to them when I really need to find out about changes to the route when there’s a Monday night game at the 49ers stadium, or want to revisit the debate about dogs on the bus. To use the “m” shortcut key, first click “Settings” in the top right corner of Gmail and select the option “Keyboard shortcuts on.” Then, when you’re reading a conversation you want to mute, just press “m.”