It seems like he would have been the only one in the position to do it (the employees were kept in the dark about a lot of things).

Most employees at most companies have pretty good grasp of things they're officially "kept in the dark" about.

Looking at the graph near the end of the article, I'd be curious to know who (Karpeles or other?) took a family vacation from January 3rd to 14th...

That should be relatively easy for the investigators to find that out.

I think that's what what the term "inside job" suggests.

Yes, but which of "karpeles" or "employee" was it?

I think pan69 parsed the sentence as

    Was the insider in the set {Karpeles, Employee}

Which is true by definition. Instead of

    Which element of the set {Karpeles, Employee} satisfies the condition (==insider)

Which is what zzleeper was intending.

This is why we should implement "xor" in natural language :D Now for the wars on if it's pronounced "zor" or "ex-or".

XOR wouldn't help much in this case. The answer to "Was the culprit A XOR B?" would still be interpreted such that the answer is a Yes or No.

True. It's more like "For condition C, I assert that a single element of set S satisfies C. Which element is it?"

This could be useful for situations like:

Question: "Was it night or day?"

Logician's Answer: "Yes"

Tell me again why we need a new linguistic construction when we have the word "which"?

"So which was it, Karpeles or one of his employees?" "Which was it, night or day?"