But more to this point is the fact that advertising plays off the information available from outside sources.

本句是倒装句，但不是你所理解的结构。

more to this point为表语，is为系词， the fact that advertising plays off the information available from outside sources为主语。主语the fact后接that引导的同位语从句，导致主语很长。为了避免头重脚轻，使句子平衡，将表语和主语互换位置，即主语后移至句末，这就是英语句子的尾重原则。

that从句结构为advertising主语，plays off 谓语 information 宾语 available from outside sources为information的定语