There should be a very easy fix for this issue if someone understands the yahoo table making instructions.
There is an optional field Called "Item info" on the Edit Grade Item pages
moodle/grade/edit/tree/itemphp?courseid=******* etc that is accessed by clicking on the edit button for an item in the Categories and Items full view.
This field places an item in the data table mdl_grade_items called item info. According to the help file for this item it is used nowhere else.
If this field was used for a grade item short name (don't even need to change the name) the problem would be solved by simply assigning iteminfo instead of itemname to the header column of the grader report. I have fiddled with this with my limited knowledge of php etc and can figure out the yahoo table building language. Does anyone know how to find the place where itemname is called for placement in the grader table? If so, it would be useful to publish this info so users could use this workaround to what is a very annoying problem that, in my opinion is the single feature that makes an excellent new gradebook module clunky and almost unusable (so much so that I now routinely download the grade data into a pre-formatted Excel file rather than work with the grade report where if I make the max column width acceptable small so about 8 or more grade items show on a single screen all I can see in the header columns in one of my classes is "Investigation" in each of the 32 columns that I have. Of course I could change the name of the Investigation to place the number at the front (e.g. 04A Investigation 04A....) but from previous experience with other courseware where I had to do just this this would confuse some students.
I think changing to the short name permanently would be the thing that I would do but it seems, since the field already exists, it should be easy to write this in as an option simply placing a selection box in the grader report preferences that assigns either itemname or iteminfo to the table headers.