A seed post is a post placed by forum staff to help give players a starting point in a new thread. This type of seed post is done once at the beginning. Once people start responding and building the thread further, they decide where the story goes. The seed post is only a starting point. Nothing more.

Or, if requested, a post placed by forum staff to help give a stuck story thread a little nudge. A thread may receive a seed post to nudge it once a month, and only the lead person in the thread may request this action.

Who is the lead person?
The lead person is either the first person to post in the thread, the thread's originator, or the first person to respond to a seed post provided by forum staff which begins a story line thread.

So, if you placed the first post to start a thread, or you responded to a start off seed post, you are the lead person for that story thread.