Q: Is every comment in the forum emailed out?
At present, the contents of comments or other page changes are not mailed out; instead the email includes a link back to the page. The mechanism for sending works like this... people can add their email addresses to a specific page (or forum as a whole) along with a time (e.g. "notify me no more than once every four hours, once a day or whatever"). Then whenever the page changes -- any change -- the notification is sent out (respecting the "once per X" limits).
Of course, for on-demand updates, the page and forum RSS feeds are your best bet.