/friend Player.1234
/unfriend Player.1234Adds a player to your contacts list or removes them. Contacts are account-wide, so you see them online regardless of which character either of you is on.
Stops a player contacting you, and reverses it again. /ignore and /unignore are aliases, and the block list survives across characters because it is account-wide.
/block Player.1234
/unblock Player.1234