With an empty scripts folder and restarting the client tell last produces the following:
(21:43) You tell Greendale '?'
java.lang.IllegalArgumentException: Invalid substring range
Note that this isn't the first tell in the list
tell last 1 and tell last 2 appear to work
here is tell last 2:
(22:02) You tell Greendale (fighting) 'back'
(23:44) You tell Sprite (idle 8min and 43s) 'Are you free to do some repairs at all?'
Ok.
EDIT: It also appears to drop tells (but not emotes)