Check glyphs do not have components which are themselves components.
There have been bugs rendering variable fonts with nested components. Additionally, some static fonts with nested components have been reported to have rendering and printing issues.
Check glyphs do not have duplicate components which have the same x,y coordinates.
There have been cases in which fonts had faulty double quote marks, with each of them containing two single quote marks as components with the same x, y coordinates which makes them visually look like single quote marks.
This check ensures that glyphs do not contain duplicate components which have the same x,y coordinates.
Is there any unused data at the end of the glyf table?
Check for points out of bounds.