Think about it for a minute. Is it really topic splitting? I would think of it as reply splitting.
However if one is seeking a new feature then I think what would be better is for a feature where a moderator uses the wrench to select the reply then chooses an option that sends a canned person-to-person message asking the user to split the reply and then the canned reply includes some options right in the message to help the user split the reply. 