So it's like Grammarly but for the tone of your message? Why stop at code review comments -- I would love to know how my Slack messages, emails, etc sound to other people.
And I wouldn't use it for the same reason I don't use Grammarly --I don't want all the text I type being sent to some third party server for analysis and storage and whatever else they want to do with that text.
It can be helpful in any text input. We decided to validate the idea on GH for the starter because most users can try it as a Chrome extension. If the idea gets some traction, it can be extended further.
Also I wish some colleagues would install this...