It's logically the same issue as with signing documents. You have to decide what aspect of the document you want to certify and ignore the rest. If you sign som

It's logically the same issue as with signing documents. You have to decide what aspect of the document you want to certify and ignore the rest. If you sign something in a complex document format you don't even know exactly what you are signing. Much of what you are signing is not even visible. Things like legal documents should be restricted to plain text... and stuff like line endings should be standardized for this purpose.