When I display a report in a web report viewer, whose service is running on a server where one or more of the used fonts are not available, the first instance of the item(s) that use those fonts is being substituted with another font. The rest of the items do render with the original font, however.

This creates confusion and inconsistency. We should use the substituted font because it's used for measuring when using Print Preview mode in the web viewers, or when rendering to pdf via print/export.