Please follow the link provide:
It suggests that it depends on permissions given to users, U can switch-off comments by un checking the permissions at wokbook level.
Hope this may help you.
I believe simultaneously the Sheets name can removed from Top?
The best way to do this is to have the admin deny "View Comments" and "Add Comments" permissions from the group or users in question. When these permissions are removed, the comments will not be seen.
If you don't want to show the sheet names at the top .when you publish the workbook uncheck the option show sheets as tabs.