The TeamPulse user has an option to add or remove subscribers to a feedback item, or other item type, through the "Add people" link in the TeamPulse item details. Clicking on "Add people" lists all users - including portal and teampulse users. If the Portal user has not provided First and Last name - one will be listed with its nickname.
Under "Followers" window - the existing followers of the item are listed. Users could be unsubscribed from here.
The list of users is separated under two tabs, depending on whether they are TeamPulse users or Feedback Portal users only.