i feel as though it would be useful to get notifications when someone comments on your post or quotes you on a post, especially for those who run art/upgrade shops. There could be a spot in the settings to turn them off if you dont want messages
The subscribe button only appears on the first post of the topic and you only have the option to subscribe to everyone posting or just the topic creator posting. I think itd be cool to be notified if one of your posts is quoted