This happens due to the font you're using, namely if we take the ProductCatalog report (it is part of the ReportBook demo you pointed us to) as example, the description textbox is set to use Arial font, which does not support Chinese characters. We have never thought of that until you brought that to our attention and we would log this in our todo list for updating.
The resolution is using font that supports Chinese characters, for example Arial Unicode and this is exactly what we're going to do to resolve this.
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