User subscribed on Q&A topic that is author of topic shouldn't get email when other user leaves comment on answer of other user

Pre-conditions:
1. At least three users should be created and logged
2. All of users should have VIEW_TOPICS and CREATE_POSTS permissions
3. At least one branch created
4. A branch has Q&A topic
5. User1 must be author of Q&A topic and have subscription
6. User2 must write at least one answer