This is an interesting one. A new client is using the Disqus service to replace the default WordPress commenting system within their website. They noticed that post authors weren’t receiving notification emails when a new comment was added to their post.
After a bit of searching, I found the following blog post which confirms the issue and provides a simple workaround for it. Normally I’d never alter the code within a plugin (as it makes future updates a nightmare) but in this case, the pros outweigh the cons.