I have checked the issue . Here are my findings :
RadGridView when exporting does not process the content additionally . It keeps it in its original state.
So when using special symbols in data, indeed the may conflict with HTML encoding.
Now the solution :
You will need to handle the Exporting event of RadGridView.
Inside of the event handler you will need to take care of escaping the HTML problematic characters ( e.g. replacing "<" with < e.t.c.
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