Can the comment field in a related table be required in crowdsource reporter?

[HenryUnderwood1]

I've got a basic crowdsource reporter published where users can mark issues and are required to set a category for the type of issue in a drop-down list (as pictured below).

There is another aspect to the app I am having trouble with. Users can also like and comment on reported issues. However, I cannot uncheck the "allow null values" option in the related table (even with a local FGDB). This allows empty comments to be added which is not ideal.

Is this a limitation of related tables? Do I need to adjust this setting before making the relationship?