They are distinguishable because they know too much. Their knowledge base has surpassed humans. We have also instructed them to interact with us in a certain manner. They certainly are able to understand and use human language. Which I think was Turin's point.
Purely retorica but, would you be able to distinguish a chatbot from an autistic human?
"It's all just PR" is a lame excuse not to think about the implications. Of things like: AI capabilities only ever going up over the course of the past 4 years.
Past performance is no guarantee of future results. It isn't just a financial cliche - if Moore's law held we would be working with subatomic sized gates instead of fooling around with EUV gates.
I've never had a normal conversation. It's always prompt => lengthy, cocksure and somewhat autistic response. They are very easily distinguishable.