As to our notion, the issue with the font styles is related to the WPF framework. RadRichTextBox is built and dependent on that framework, so I am afraid that there is not much we can do in this case. What are the applications you mentioned that work properly? Are they WPF applications or are different?
The public item you have encountered is related to the Document Processing libraries. These components are independent of platform and don't have UI. Therefore, the nature of the issue in this context is different.
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