I’ve just enabled the comment_notify module, which adds a checkbox at the end of the comment field for “notify me when new comments are posted”.
I’m experimenting with other modules to add more functionality, hopefully without making migrating off of Drupal in the future a disaster (I plan to migrate us off of Drupal eventually, but the amount of time required, and the amount of time I have are not at all compatible). We also have the (very real) problem of keeping the bills paid and the awesome problem of getting Webmin 2.0 out the door this year. You’ve all convinced me that you hate Drupal; I believe you…I just don’t have the resources (time or money) to fix it. Since dropping prices and switching to monthly billing, our revenue is way down (even while number of sales is way up…it may even out eventually, but in the short term, we’re running really lean around here).
We do need (light) moderation (mostly for spam, not for aggressively getting rid of posts even if they seem repetitive for old-timers), from some trusted members of the community. Are you guys volunteering? (We’d have to talk out and document what moderation policies would be, if we extended it out to non-Virtualmin staff. But, I’m more than happy to have some help around here. We’re pretty much always overwhelmed.) 
We, of course, need some better tools for moderation, as well…as it stands, even me and Eric can’t do a lot about some kinds of organizational issues, but there are facilities to move posts (if they’re in the wrong section), unpublish posts (if they’re spam, though we also need to know about it in the tracker, so we can ban the user entirely), and make sure they have good titles and aren’t bringing back ancient dead threads (though there’s no way to re-deadify a thread that’s been revived in this way, even if we could move a comment off of an old thread). But, we can ask users nicely to post a new topic when they have a new problem. A lot of times, someone sees an old error and think it looks kinda similar to their problem (even if it was 10 years ago and clearly, to us, has nothing to do with the problem they’re seeing).
Anyway, I’m doing the best I can. I hear your frustration. I’m frustrated daily by Drupal issues, and lack of time/money to solve them. Let me spend some time with Advanced Forum module and get back to you in a day or two with whether we can run with it…it’s a very big, intrusive module (exactly the kind I hate), and overrides themes and such in ways that are probably disastrous without a ton of work…so I may not be able to flip the switch on that without doing a lot of work. Avoiding having to theme the forum separately has always been part of why I don’t want to use a standalone forum (though nowhere near the most important one…the most important is that I don’t want a separate notifications system, but since Drupal can’t get notifications anywhere close to right anyway, and configuring them appears in a half dozen places even when you only handle them via Drupal, it’s pretty much pointless to use that as a reason to stick to only Drupal modules, I guess).
OK, enough rambling. Tell me if the comment notify feature helps address the subscription thing. I’ll keep trying other subscription options, if not.
cheers.