In the Apple Support Communities someone reported they were seeing the Japanese version of Han characters when they should be seeing the Chinese version. This can happen because the default Han font used by iOS for plain text is determined by the order of languages on the list in Settings > General > International > Language.
To make sure the default font is for Chinese, one fix is to switch the OS to Chinese and then back to English, which should put Chinese in second place on the list. Info on how to switch languages when you don't know one of them can be found here.
Even with rich text where correct fonts are specified in the markup code, Mac apps may not recognize them if they are not present in OS X, and the same fix would be required in that case.
An example of the difference:
Japanese Version 所 and Chinese Version 所.