I'm sure it was just a poor choice of words. I know Dimo's goal is to help you find your solution as quickly as possible.
In any event, it appears you've found the solution to your problem. I think what Dimo meant to communicate is that the RadGrid does not impose any special font styles (such as those you posted earlier), so the problem had to exist in some other custom styles in your app. Hopefully that helped guide you to your custom skin file and your solution.
In the future, you may be able to more quickly debug these weird CSS issues using FireFox and FireBug. That tool makes it very easy to see where styles applied to a specific control are coming from. If they're in-line styles (as they were in this case) or styles not coming from a Telerik CSS class name, you know to focus your debugging in your custom code. I use the tool all the time and it makes life a lot easier!
If you have any trouble in the future, you know where to find help. 'Til then, enjoy the RadControls!