I’m having the same problem as azmatt, who opened this thread. Other people’s comments to any author’s thread are emailing perfectly well, but when an author comments on their own post it’s not getting emailed.
I suspect there’s a bit of code that’s suppressing emailing post author’s comments to the post author, rightly believing ‘they know that, they wrote it’, but it’s screwing up comment notification for everyone else.
So, there’s two problems in this thread: one is (I’m guessing) comments being suppressed, and another is the emailing functionality from various web hosts.