You can make the comment required by all users by doing the following:
1. Login to your Journyx site as your admin user account.
2. Go to Config > System Settings > Entry Sheets
3. In the Global Settings section you will find an option that says "Allow users to create entries with empty (blank) comments"
4. Uncheck that box and click save at the bottom of the page.
That should require comments on all entry sheets.