When you leave the comment(s) section empty and try to post a comment, you see a blank page with the following message:
Error: please fill the required fields (name, email).
I wonder if this can be integrated to be displayed within the comment page itself and not on a page by itself. If I remember correctly, WP has done this since many previous versions. Any chance to integrating this along with the comment page where the user tried to enter the comment? It would just be visually better to do this.