Autodesk Revit only supports TrueType fonts. This extends to OpenType fonts that have TrueType outlines. I know firsthand that TektonPro is an OpenType font that uses PostScript outlines and therefore cannot be used in Revit. I cannot say for certain what the problem is with the Graphite font, but I suspect the same is true. You can open the font file to confirm this yourself.
Here is a link to a related FAQ. This doesn't have any more information that I didn't already give you, I was just happy to find that it exists.
For the record, Kevin Hawkins is not an Autodesk employee, I am pretty sure he works for KarelCAD one of our Australian resellers.