Yeah, that could be clearer. What initially struck me, before I'd finished reading the article, was the impending sense of post hoc ergo propter hoc. So my response, at that point, was to invert the relationship between copying and pecking order: a) "pecking order is an effect of copying" vs. b) "copying is an effect of pecking order."

If b) is the case then it makes sense to frame the issue as "The way people copy each other's linguistic style reveals their pecking order." But if a) is the case then the article's conclusion is tautological. Of course you're right that that doesn't stop us from taking it as a direct measure of power or influence, since they're still strongly correlated. I was just thinking of it more as a measure of linguistic reserves [1].

[1] http://goo.gl/NOUwo (Sorry to use a link shortener, but it's a long Google Books URL.)