How to provide email notifications to admins for *all* comments? My site admins are asking to receive email notifications automatically whenever a comment is posted on any content on the entire site. I already have comment_notify enabled, but that only allows them to get emails for comments posted on their content, or on posts they have subscribed to. They want to get those emails for all content by default.

I have also seen the "Notifications via e-mail comparison" page, but none of the module descriptions say they have this feature.

Am I stuck with having to implement a Rules based solution? Or am I missing something?
I see that you've already found the Comment Notifications comparison page over at Drupal.org - but also that you say you have not found the module you're looking for there.

However, from the description of your requirements, it sounds like the Notify module is pretty close.

Since it uses a digest format and depends on cron, it will not give your site admins instant notifications of new content, but otherwise, it matches your description.  Most important, It will send out notifications about all new comments, all new nodes, or both.

Disclosure: I am a co-maintainer.