Hi, how did u converted your desired Q&A data into simple linear Q&A database? Thanks
Practically it can be done by doing some changes. But there are not any simple steps for this. You can look in both notification and hook into BP or AnsPress notifications.
As I said a few minutes ago in a question, this will be fixed in 2.4. Currently working on same issue.
This will be fixed in 2.4
Its already exist in user profile -> subscription. You can check template in user/subscription.php
Did you tried this POT ?