I just noticed that notifications for replies to comments/posts are disabled by default, to enable them you just need to go to your settings and check the relevant boxes
It might be a good idea to have comment replies turned on by default, I feel like it'll help drive discussion/engagement but that's ultimately up to the devs
I have heard a request to make these default has been accepted so it's in the works.
In the meantime if anyone want to know to turn them on, head over to my post on m/quickstart.
I also think enabling those is a sane default. Its just what users expect.