Alerts on Comments in Modern Pages?

Hi Gretchen, happy to share if it's useful. 

The solution that I got working for us works as follows:

1. Powershell script, running as a scheduled task, periodically reads the comment count for all News items (List A) on a given site. 
2. The comment count is compared to the comment count stored on a separate list (List B).
3. If there is a comment for a News item that previously had no comments then a new item is added to List B with the article URL and the number of comments. If there is an additional comment for News article that already had comments then the list item in List B is updated.
4.  List B has an alert setup, going to our team Distribution List, whenever List B is added to or modified, which sends an Alert email including the URL of the article.

I don't know if that works for what you are trying to do. I have the script running on my local desktop as I had real problems getting the script task to run on a server with any sort of encryption. That may be a problem for you. Likewise, in my solution there are only ever 4 possible authors of the News items so for now I can send an alert to all 4, if you have lots of potential authors that may be no good, although I don't think it would take much to change the script to send an email to the article author once a new comment is found.

Hope that helps. Script attached (hopefully).