Line [Thin] is a pen that can be used to make thin & thick lines depending on the Pressure you're putting.
You can change the settings of the pen however you like.
If you want to disable the Sharpness then go to 'Sub Tool Detail', then to 'Correction' and disable Sharp.
If you want to disable the Sharpness then go to 'Sub Tool Detail', then to 'Correction' and disable Sharp.