[paldepind2]

In my humble opinion the SO question and some of the comments here conflate "expressive" as it's used when talking about the theory of computation and "expressive" as it's used when comparing various high-level programming languages. The former has a very precise (but also quite narrow) formal meaning and the later is just the normal English work "expressive". They mean very different things so I think it's a bit unfortunate that we use the same word for both because some people get the idea that they're somehow related when they're really not. I mean, in a way regular expressions are more expressive than turing machines but turing machine are more expressive than regular expressions.