Possible Clues:

• Gas, including oxygen, beginning to materialise? It's not important
• 'It isn't a big deal'
• Gossip about doctor turning up? It's not important
• Gossip involving old maiden? It's not important
• Chat about decoration that's unimportant
• "Never mind!"
• What a shrug might mean
• Regardless of what's in a vacuum?
• It's unimportant gossip about old medium
• Gossip about old medium? It's not important