To reproduce...

1. Choose or create a course and add a gradeable activity (e.g. Assignment). Also add a few users.
2. Go to the Gradebook and export in text format - default values are fine.
3. Open in a good text editor. I used command line 'vim'. Note that the export is fine
4. Add a turnitin activity to the course.
5. Repeat the export
6. This time - note the BOM has appeared in the header item immediately before the turnitin activity.

The appearance in Vim is thus:

First name,Surname,ID number,Institution,Department,Email address,Assignment: Dummy activity<feff>,Turnitin Assignment: Test turnitin

The '<feff>' is the character for a Byte Order Mark.

When exporting Excel files the file is completely corrupted as a result. I have not (yet) checked this with Moodle 2