When using tab to autocomplete <entity> and <dataTag> and even after dataTag, the autocomplete will always put the player's name in.

Steps to Reproduce:

Go into a singleplayer world
Type /entitydata in the chat, then press spacebar,
Press tab as to autocomplete the <entity> argument.
It should come up with your player's name
Press spacebar.
Press tab as to autocomplete the <dataTag> argument
It should, again, come up with your player's name
Keep repeating spacebar, tab, spacebar, tab, and it will keep coming up with your player's name.