Probably your default template was somehow changed.
You can fix creating a new template for the default page without the undesired features.
This is a way to do it:
- Open a new empty document
Tools
>Options
>LibreOffice Writer
>Print
>Comments
>None
Then follow the step-by-step procedure to change the default template from the wiki page of Libreoffice [1]:
- Choose File - Templates - Save As Template.
- In the New Template box, type a name for the new template.
- In the dialog that appears, double-click the "My Templates" folder, and then click Save. You will then be prompted for a name; write it and click OK.
- Choose File - New - Templates.
- Double-click the "My Templates" folder.
- Click on the template that you created, and click Set as Default.
- Close the dialog.
Alternatively you can purge and install again Libreoffice, or hope that with the next major update the default template is overwritten, but I think to this is [2] "to break a (butter)fly on the wheel".