The integration version of Trello import/export doesn't allow importing comments from Trello cards that existed prior to the integration/sync. This prevents us from retaining significant discussion about a feature (or idea) in the Aha copy of the information. People often elaborate on the idea in the Trello comments or we have questions back and forth between the PMs and the people submitting.
The Trello integration supports syncing with Trello Cards and Trello Checklist items and the fields associated with them directly, but not the activity feed on the cards. It would be great if you could add this!