I created a new gradeable Text/Numeric and gave it 0 numeric fields and a single text field called "Notes". This seems like a pretty typical use case for having a general note storage for instructor use (or TA use).

In Fx 52.0.1 and Chrome 57.0.2987.133 on Win 10, when I go to put in "grades", the view looks strange. The total field is very wide and shows under the "Grades" heading, and then the Notes text field is very small and shows where "Total" should be. The text heading, which is pretty wide, is then empty.

Looks like in the 0 numeric fields case there's no dummy cell created. In my opinion, the "Grades" heading shouldn't even appear if there's 0 numeric fields, but if you don't want to change the headings, then a 0 numeric, 1+ text fields form gradable should have empty cells so the table aligns correctly.