I too have registered just so I can so I add my voice to state how awful I find this update for those of us who work as editors with longer and more-complicated comments. My work never involves using comments as a means of having conversations with people - I am providing information in the comments.
The biggest issues I have are around editing of comments and spell checking; I am significantly held up in my work by the excessive number of clicks I have to use to edit a comment. I need to be able quickly edit existing comments, which is a frequent part of my work. Also, the removal of the formatting in comments is an issue as I often need to use e.g. superscripts.
Then, if I have a comment, I want the spell check to work on all of that comment, not only on the half of it that has changed.
This is a really retrograde update for many users.