In regards to the not being able to distinguish thought speech debate.
I recently reread The Hork-Bajir Chronicles, and when Aldrea morphs Alloran, she uses thought speech, as well as her appearance, to fool the guards in to thinking that she is Alloran. When she uses the computer, it also says something about thought speech recognition, knowing the voice was Alloran's. Haven't got the book to hand right now, but I'm fairly sure that was the case.
And, with that in mind, the idea of thought speech becomes even more confusing.