As for Harkle Harpell's eyes being teleported away from his body, he actually had an excuse that time: it happened during the Time of Troubles, during which everybody's magic spells went wrong somehow. Harkle tried to teleport his entire body before he knew the situation, the result being that he was able to see his intended destination (since his disembodied eyes were there) and talk to the people there, but his body remained behind. He was blind to his immediate surrounding until his colleagues were able to help him make the trip overland and reinsert the eyes in their sockets.