Subscribe to the whole thread rather than to replies to your comments only?

But why tho? I'm not joking, just genuinely curious as to why would you want to see all comments displayed like that instead of just checking what's the most recent or the ones replying to you directly, there's a good chance that many of the comments that aren't in the last couple of pages are simply people having a conversation or addressing old stuff. If it's relevant to everyone most users will have the common sense to post it at the very end to make it visible.

Edit: now that I stop to think about it, it would be nice if we had the option to get notified whenever someone adds to the conversation even if they're replaying to someone else. By conversation I'm referring to the indented replies instead of a new comment at the bottom, don't really know what's the name of those.

+1 Don't really understand why such a basic function isn't already present.

You could try ESGST, it has a similar functionalities: mark comments within a thread as (un)read, go to first/next unread comment etc.