I have a lot of like/hate feelings about sub-replies. Sometimes they are super handy to have a quick reply to a previous comment without diverging the main thread. However, I users use them a lot as a way to continue the conversation in the main thread. This is annoying because you cannot see these replies in the Feed. You have to click in order to see the latest.
I have two ideas that I could make this better...
A long time ago sub-replies used to be displayed in the feed. An option to bring this back would be nice.
If #1 is a no-go, then I would like an option to disable the ability to add a sub-reply. If this is done though, we would need to make sure that existing sub-replies that have been made are still accessible/readable.