What works best for us is to have the AI recipient input their reason/notes into the AI notes. Our approval process captures those notes with gel and includes them in an email back to the idea submitter and populates them in a custom read-only Approver Notes field.
It's not as clean as I'd like, but the approvers like not having to navigate away from the AI to enter notes and the client team likes the fact that they can access the notes directly on the idea.