Hello. I am using Odoo Online (saas-18.3). 

Currently, any user can mark as done, edit or delete the tasks, even the ones assigned to other users. I want only the asignee or asigned to be able to complete the task.

The ACL is set as:

Name: mail.activity user 

Model: Activity

Group: Internal User

Access rights: Read, Write, Create, Delete

And there is a record rule which I would assume should solve my issue but it´s not:

Name: mail.activity: user: write/unlink only (created or assigned)

Model: Activity

Group: Internal User

Domain: ['|', ('user_id', '=', user.id), ('create_uid', '=', user.id)]

Access rights: Write, Delete

Not sure if I am missing something. I also find it odd that this is Odoo´s default behaviour with tasks?

Thank you.