What about two different fields entirely?
Ban type: <Default selections and times>
Reason: <This is manually typed in by the banning staff member and will be displayed to the user. If left blank, the "Default selection" will be set as the reason>
Admin Comments: <Comments about the ban, like how "Reason" is currently used, and might even make it easier than having to also opencomments of a player just banned and insert basic details of why they're banned>
