This is indeed a problem with the converter's engine- NRefactory. In fact, if you try the conversion in the simple code coverter hosted by the ShareDevelop project (the people that enhance NRefactory), you'll see the brackets problem exists there, too:
I'd suggest that you share your feedback with the SharpDevelop/NRefactory community and see if there are any plans to improve the engine. As soon as the engine supports this conversion, we'll be sure to add the support to the Telerik Converter.
Hope that helps!