Replication steps:

1. If you go to a course where course completion is enabled and set up
2. Find the "Course completion status" block and click on "View site report".
3. (Optional but saves time) choose one of the visible groups from the popup (eg "8732_2_02_Phill").
4. Scroll down to the bottom of the page and click "Download in Excel-compatible format (.csv)."
5. Inspect the resulting file.

What I get is attached and the pattern is the same whether you filter on a group or go with all participants. There are two problems:

a. There is no header row.

b. The first data row has a blank cell and everything else is shifted right by one cell.

Given the variability of this report (completely dynamic depending on whether any activity has a completion set on it), a CSV without header rows is useless so I'm disinclined to accept any argument along the lines that header rows are only a convention and not a required part of CSV.

Shifting the data right by cell one suggests "something else is going on" such as a call to output the header row not working and emitting a blank field. In any event, that really is a bug.

For the record, the UTF-8 variant has the same problem.