There's no rule as such, but we're generally asking people to refrain from posting in excess. Other people don't have three ongoing topics of their own at the same time. Use common sense.
Sorry but joining in are not "butting in on numerous other conversations". Is that a community forum or only the admins has the right to forming their opinions or give advice, answeres, ..?
Dear (Mr or Mrs) Paymeout! Have you anything against that i joined to your topic?! Am I distruptve to you?