This is a meta issue for the requirements for the Comment field on the Workflow transition object.
#2597986: Allow customizing the Workflow Comment field, like core Comment does
#2850103: Display/hide/require the Comment subfield based on state
#2192305: Convert Workflow comment to core Comment field
#1907960: Helper issue for "Comment field"
#2121757: Assess Comment alter
See also the following Meta issues:
#318325: [META] Display/hide/require the Widget subfields based on State/Role
#2639372: Set entity fields to hidden/view/edit/required based upon workflow state
Comments
Comment #2
johnvComment #3
johnvComment #4
johnvComment #5
johnvPlease see also #2948377-20: Do not hide widget when having only one option
Comment #6
johnv