What happens to the personal data when the user is removed from the company acount?

The data will be retained as it is.

The shared document will remain as a shared document (the same applies to the comments).

However, if the user is removed from the company account, the user account will be deactivated. 

Please contact the Customer Support at support@yaraku.com to activate your account.

Please refer to this FAQ for how to login again after the account was activated again.