Digg will begin sending emails alerting users when someone replies to their top-level comments.

Community manager Jen Burton said in a blog on Digg:

You know those amazingly witty comment replies you always post on Digg? Does it sometimes seem as if the original commenter didn't see them? Based on your feedback, we're releasing a small feature that will send an email to that original commenter—now you'll know for sure if they're ignoring you. We're hoping this new feature will foster even more communication and sharing within the Digg community.

Now, once someone replies to your top-level comment, you will be notified via email with the text of the reply. Note that this will only occur at the original top-level comment, not on nested comments. Meaning, if your comment spawns replies to replies and so on, you will only receive replies to your parent comment. We think this is the right balance and definitely don't want to clutter up your inbox, so if you prefer not to receive these notifications, you can easily change your email preferences.