The social tagging features of SharePoint Online are available to site users by default. However, you can change that availability for specific site users or groups by removing their permission to access these features, which include the ability to:
Create a My Site by clicking About Me in the header for the first time.
Follow people’s activities and related information.
Use Tags and Notes.
For example, if you don’t want specific users to be able to add tags and notes to web pages, you can remove their permission to do so. Without access permissions to social tags, users or groups can’t use social tagging features.
You must have permission to use the Office 365 SharePoint Online Administration Center in order to perform this task.
To remove permission to access social tags for a site user or group:
Click Admin > SharePoint > user profiles, and then under People, click Manage User Permissions and type the user or group name in the Add or Remove box. In the Permissions box, you can select Use Tags and Notes and other social features that you want to allow for the user or group. For more information about this task, see Manage personal and social features.
Note: After you disable the social tagging features, tags, notes, and Like features appear dimmed (unusable) in the ribbon for document libraries and lists, and on browse pages in a site. This is because the SocialRibbonControl feature, which regulates the display of these controls, is enabled by default in SharePoint Online and cannot be configured differently for individual sites.