I've seen many examples of where a person makes another thread that was almost like another one. For example:
"Pie or Cake?" Then there's another one called "Is Pie sweeter than Cake?"
So, I was thinking, that a moderators can change the topic of a thread if it's getting off topic. Like, posts something that can't be ignored. So now you can talk about two slightly different things in one thread instead of creating two threads that talk about basically the same thing.
I know what you're talking about... it's like in the Tavern, there's a thread called "Let's talk about Miley Cyrus". Then, someone posts "who hates hanna montana".