Martin,
Thanks for checking out the site and SHHS dataset. I think the variation in the number of commas on each given line that you're seeing derives from the "Comm" variable/column. "Comm" is a free text field that includes scorer notes about the overnight sleep study quality. Some of these notes include commas. That said, these field values that contain commas will be contained within double quotes, which most CSV parsers should understand. The dataset reads into Excel, SAS, and R correctly for me.
Example snippet from "Comm":
1,0,0,6,"Lot of alpha-delta sleep but not alpha intrusion. Sleeps on back entire time, only change in position when awake. Airflow choppy at times (-1 hr), chest very small amp (- 1 hr), Low baseline saO2 ~92%, Desats into 70's in REM.",0,8,8,8,8,8,8,
Here's a Stack Overflow post that describes handling commas in a CSV file.
Hope this helps!