It would be fun to have a Slack bot that could be copied late into a long email thread of reply-alls. It would create a channel or join an existing one, parse the thread into a conversation with messages applied to people in the conversation, and then reply-all to the email thread with a link to the conversation in Slack.
This would allow you to politely suggest a conversation move to Slack and move it there at the same time.
See also: the same, but with a new GitHub issue.
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