For one who has started threads myself, the answer is that you're not required to sub to the starter of a post, that's up to you to do so. The starter is the one who creates the title of the topic, so if you are looking for subs than the best thing would be is to subscribe to the starter of the post if you're not already.
Also even though as I was thankful for people subscribing to me because of my thread, it was great to know that other people were getting subscribed to by others because of the thread that I started.
I hope that answered your question.
Nigel Parkinson, Jr.
Creator of Comic "Pets Allowed"