Customer Comments : how to prevent that ?

Customer Comments : how to prevent that ?

Currently on the helpdesk portail the customer can 'comment' instead of reply.

The issue is that action is not interacting well with ticket status : as it is not a reply it will not switch back the ticket to 'Open'.

How do you manage that ? Do you know if there is a way to prevent this 'comment' function on customer side ?

THANKS !