Steps:

1. User A creates forum topic.

2. User B replies to it.

3. User C replies to it (and user A and B gets email)

4. User B replies to it (but unchecks the send email notification checkbox when creating post).

5. User D replies to it.

Actual Result: User B still gets email after User D posts a new reply

Expected: User B should not get any more email from that forum topic.

Similar bug in another scenario.

Steps:

1. User A creates forum topic.

2. User B replies to it.

3. User C replies to it (and user A and B gets email)

4. User B edits reply to post created in step 2 above (and unchecks the send email notification checkbox when creating post).

5. User D replies to it.

Actual Result: User B still gets email after User D posts a new reply

Expected: User B should not get any more email from that forum topic.