Question: Our errbot is providing links to JIRA tickets when it sees the right ticket patterns. Unfortunately, in slack it is common for users to edit their posts, and if both edits contain the JIRA ticket pattern, errbot provides the link twice, it is annoying. 

Can I detect when a message is an edit as opposed to the original message?

Answer: 
Now you can because from the .extra argument on the messages you can get the message ID from slack.
This is not currently possible (on any of the backends), no. For chat networks which allow editing of messages, errbot currently injects edited messages as a new message.

If you need this functionality, please open an issue on errbot's issue tracker so we can brainstorm about how to possibly introduce this functionality.