We want it to be known that speaking more than one language can be a pain sometimes. Sten in Swedish means stone. That being said, Sten is a legit name in Sweden, but still Sten the stoneface fits a bit too well.
Maker, even Kristen Stewart has shown more facial expressions.
Besides that, he still is one of my favorite companions of DA:O. Despite (or because) him being a stoneface I thought him absolutely hilarious at times.
I seen more expression in EDI
The flying carpet from Aladdin has more emotional range...(sorry Sten ^_^')
It's because his expressions are too subtle for unenlightened beings.