You can’t restrict notes or sticky notes access by site.  If a user has access to add notes to a customer or customer order, then they can see all other notes added.  It isn’t a site specific related permission, it is all or nothing for a given permission set.

Sticky notes are the worst way to manage this sort of information anyway because they are easily removed or lost.  Not to mention they are not available in any Aurena client so will be going away in the future anyway.

If you need site specific methods of storing note information, the only way I know out of the box would be to use DocMan with specific site driven document classes restricted to each site.  That becomes a lot of IT Admin to manage that level of control.

Alternately, you could create custom fields for each site, and restrict them to a certain group, but here again, you would need to manage at the user level for each field who can look at them which is still pretty tricky.

Many thanks for this feedback, an excellent answer, much appreciated. 

Thank you so much!