The "add comment" use case needs to use the text policy validator to set the "needs moderation" state.
If the comment needs to be moderated, the public flag must be set to false.
Also, the message below the comment field must reflect the state of the comment display, as outlined by the old code: https://github.com/wmde/fundraising/blob/master/src/Controllers/ActionController.php#L111
https://github.com/wmde/fundraising/blob/master/src/CommentHandler.php
In the new app, the returned text must be translatable