Some of the more active users have commented that they haven’t received notifications when someone replies to a topic they posted on, unless they were explicitly mentioned or the reply was directly to their post.
Looking into this further, I realised the default notification when you reply to a topic was set to Tracking but should really be Watching so you don’t miss any replies. I’ve updated this setting so you may see some more notifications than before.
If you prefer a different notification scheme, you can override the defaults in your user profile. You can also change notification defaults per-topic, if you prefer to follow more (or less) of the conversation.
For more information, please see Managing and subscribing to notifications.