Is there a rule that says I cannot deliberately make two separate posts on two separate subjects in succession in the same thread?

If not, then why would a CL arbitrarily decide to merge them without asking me first?

If I wanted a single post, I am perfectly capable of doing that myself, so if there is a rule that says I have to do that, please explain. Otherwise, how can I prevent a CL from changing my posts to something different than I intended?