CSV Separator is not always a comma and this has to be considered when Sakai exports data to be imported by MS-Excel. I have solved it by a new property in sakai.property named csv.separator. I've set the default value to comma so that if the parameter is missing, Sakai will behave as currently. With this jira, you can find the patch for trunk.
From my point of view, CSV separator is related with locale settings. For example, in Spain we use ' ; ' as we use comma to separate decimal digits from integer digits in a decimal number. The problem then is to decide if leaving this setting at sakai.properties is enough or if it should to moved to user preferences.
Hope this helps.