Activity (or comments) as a field

I just got asked to add a “Comments” field to one of our tables. This struck me as off since we already add comments to the card for a field on a regular basis. It would be useful if one of the field choices was either “User Entered Comments” where the field is a reflection of any user comments added to the card or vice versa anything entered in generates a new comment that can be viewed in the history or for the field to be a straight lookup of any comment (or last activity0 that was entered into the card. This would reduce the duplicate nature of the request and be highly useful for surfacing comments (or adding them as an input). Thanks