Formatting in Notes

Administrators can allow formatting in notes:

For administrators this also applies to Instruction elements on forms and profiles.

Enable

Set Use RichText Editor for Notes on the Admin > Site Settings page.

"Yes" will enable it for all users unless they set their preference to "No".

User Preference

If the Rich Text Editor is enabled by site administrators, each user can decide whether to use that on their My Preferences via Use Rich Editor for Case Notes (if enabled on your site).