we have been discussing the idea of email notification - theres a ticket on open about it assigned to me. I think and so do a few others that email is to invasive and so an RSS is the way to go. I have written up a little method that seems to work for me :D
Check it out at http://pastie.caboo.se/187947. Pretty simple function, just select the comments as dataobjects and output to an RSS feed!
I have that in the Page_Controller class and to view / subscribe its available at yoursite.com/home/commentrss.
If you have any improvements on it that would be great to hear!
EDIT: this is actually built-into silverstripes page comment class. I should have looked more throughly - Visit yoursite.com/PageComment/rss to see the latest comments. No need for custom code