With the used 2014.1.225.40
version a bug has been introduced due to which the stylization of plain text has been added to the body element as you described.
This bug is fixed in the 2014 Q1 SP1 version. I suggest upgrading the used Telerik dlls and verify if the described scenario behaves as per to your expectations. Also, you can test the latest availabe version of the RadEditor with this online demo
and test how the style formatting is applied.
If you still have difficulties with this issue, please provide a sample configuration demo, so that I could investigate the exact scenario locally.
Check out the Telerik Platform - the only platform that combines a rich set of UI tools with powerful cloud services to develop web, hybrid and native mobile apps.