Methinks the sentence does not sound natural. I also think that there should be confirms instead of confirm (source):
That the messages are written in simplified Chinese—Hong Kongers use traditional Chinese—confirm that the intended audience is Chinese tourists.
I would rewrite it by changing the word order:
That the messages are written in simplified Chinese—Hong Kongers use traditional Chinese—confirms that Chinese tourists are the intended audience.
Other than confirm, is the original sentence correct with regards to the word order? Does the rewritten sentence sound more natural to you?Is it correct? If not, how would you rewrite it?