Add filter before checking comment in wp-comments-post.php

[sgrant]

Hello!
We'd like to allow our users to submit WooCommerce ratings without being forced to write some text. Some people find this intimidating (they like or dislike the product, but can't or won't say why).
I've attached a patch that adds a filter immediately before the empty string check in wp-comments-post.php. This allows us to hook in and change an empty field to something simple (say, a single space) while maintaining WooCommerce's rating metadata. Is this reasonable for core?

[sgrant]

Add a filter before the empty string comment check.

[ocean90]

Closing as a duplicate of #16979 since this would affect the duplicate comment checks, which is handled by #16979 too.