Mention in a comment of a question or answer doesn't generate in app notifications

Summary

Using the latest version of Confluence Questions (2.6.6) when adding a user @mention to a comment of a question or answer does not raise a in app notification in Confluence, email notifications however do work.

Steps to Reproduce

1. Create a question or answer in Confluence Questions
2. Comment on a question or answer using an @mention

Expected Results

User should receive a notification as stated in the notification drop down:
(New notifications will appear here when other users:
Mention you within a comment, page or blog)

Actual Results

Only an email notification is received.

Notes

I found two other DEV issues that are seemingly related:

CONFSRVDEV-4163
CONFSRVDEV-4203

It's also not clear anywhere if this is an expected behaviour or feature of the Confluence Questions add-on.

Workaround

No known workaround.