Non-translatable fields error when using: Content Moderation + Content Translation + Comments

Steps to reproduce:
1. Install Drupal 8.5.x (8.5.1 in this case, was working fine before 8.5)
2. enable Language, Content Translation, Content Moderation, and Workflows modules
3. add another language, like French
3. enable content translation on Basic Pages
4. add Default Comment field to Basic Pages (not via "Existing Fields")
5. add the Editorial workflow to Basic Pages
5. create an English Basic Page
6. translate that Basic Page and try to save

Expected behavior:
The node saves.

Current behavior:
You get an error saying "Non-translatable fields can only be changed when updating the original language."

Current Work-around:
Edit Baic Page Comment field and check the "Users may translate this field" checkbox. Now your Translation will save.

Issues:
* The error is not very clear and if your dealing with more than a few fields (like 50) this can take quite a while to debug
* Doing the above steps in a different order (say adding the comment field first, then enabling translation, or adding the existing Comment field) will not trigger the error as the checkbox get automatically ticked when following this order

Proposed Solutions:
(a) remove the "Users may translate this field requirement" for comment fields. After all, what does it mean that users can translate this field? It is not the ability to translate comments, or field meta-data like title and description. This field merely binds a type of comment to a type of node, right?
(b) Have a better error message telling users what field is the offender in the error message (or in Drupal logs)