question

>> Firstly, it would appear that accounts are being added to each other's friend list automatically. I've noticed this with accounts that are friends on Steam. I'm not against this per se but is this expected behaviour? I haven't sent any AddFriend requests as of yet.

According to this document, it says that “In the event that a player has linked their Steam, Facebook, or Xbox Live account, their platform-specific friends can also be displayed, if those friends also play your title.” So it is an expected behavior.

>> So, if it has been added automatically, it presumably hasn't been added completely - enough to appear in the GetFriendsList request but not enough for RemoveFriend.

Steam friends is a field to record the friendship of Steam platform. Those friends are not added on PlayFab side. It is temporary and friends from external services will disappear once the access token is expired. So you can’t remove it, but you can decide whether to show it. API GetFriendList has a Boolean parameter named IncludeSteamFriends, it is by default set to true. If you don’t want to show Steam friends, you can set it to false.