If the tax question is complicated by someone's status of being an expat, then yes - I'd be inclined to allow it. But you have to watch out for it.
As an expat, who should I pick to do my US taxes?
.. that's bad.
I have a question about the US expat deduction and earned income credit
... that's equally on-topic here and on Money. Either site could have someone with experience taking the deduction, or someone that just happens to know a lot about taxes. It's up to the author where they put it, and we should respect that.
What is a mutual 'no double tax' treaty and how do I deal with it while filling out all this darn paperwork?
Definitely on-topic, recent treaties now require people to file in two places, yet pay in one. Yet many are delightfully ambiguous. Last year you didn't have to file in the country that you reside, this year, you might, but depending - can they make it any harder?
I have a question about earned income credit (that isn't complicated by being an expat)
... Off topic -> Tell them we do entertain some financial questions, but they need to have this sort of bizarre twist due to being an expatriate.