This issue has been there for about a couple of months.
If we submit inline comments only on a diffusion commit, no email is sent (check https://secure.phabricator.com/mail/query/outbox/).
See {rHGTEST0e1f30ecdeca} and {rHGTESTa5d6d422f8b3}.
If we submit some text in the comment panel at the bottom of the commit page along with the inline comments, an email is sent.
See {rHGTEST3b70277d773b}
Is this an expected behavior or a bug? If this is expected, is there some configuration option to turn on email in this case?