This turned out to be the expected behavior of the WPF CheckBox control. It treats each first underscore character as a mnemonic symbol and displays it below the following letter only if the Alt key is pressed (or the system is configured to always show them).
I managed to avoid this behavior by wrapping the text in a textblock, which is set as content of the checkbox. This fix will be part of the upcoming internal build, expected most likely next week.
Thank you very much for bringing this issue to our attention.
the Telerik team
Follow @OpenAccessORM Twitter channel to be the first one to get the latest updates on new releases, tips and tricks and sneak peeks at our product labs!