Is there a way to only allow members to comment on trello boards?

[Veronica Rigatti]

I know that commenting can be disabled, but is there a way to allow commenting only. So members can comment but cannot edit the board or cards as far as changing descriptions, checklist, labels, etc. ?

[Iain Dooley]

@Veronica Rigatti the best way to allow commenting only is to add people to a team, make the board team viewable and then enable comments for team members.

[milynnus]

@Veronica Rigatti  Intra board permission at this specific level does not exist. In a course delivery platform that I built, commenting is disabled from learning board but allowed on the classroom board by the same topic list as the course. So you think you can have shadow cards linking back to the main where the restricted users may be observer (available if on business class) if you want comments to go back to the main board, it can be automated through the link. I cannot however confirm that can be done with Butler only. My focus is on things beyond Butler. See example. 
https://www.loom.com/share/67c10b64313f4ef0aa0c7602251b125a