BTW, I recently upgraded some this and that on the back end of the blog, and it does seem to make comments post much faster - and unanticipated benefit.
For WordPress self-hosted people, there is already a "restore legacy editor" plugin, even though Gutenberg hasn't been installed yet as the default.
I thought you were on WordPress.com, not self-hosted WordPress. I can't find any info on WordPress.com and Gutenberg or Gutenbergerish editing, so I don't know what to tell you. It may not be an issue for you at all.