The parent doesn't propose to "expand the definition of the word 'troll' to include 'authors decrying trolling'". He proposes defining trolls as "as anyone who posts inflammatory, bad faith, needlessly aggressive, insulting, false, or otherwise unproductive content".
If you assume that the word troll does not mean "anyone who posts inflammatory, bad faith, needlessly aggressive, insulting, false, or otherwise unproductive content" then someone claiming it does is pretty clearly expanding the definition of the word.
Which is as (or close) to how it has always been defined, and how the authors of TFA use it.
I actually disagree with both of these assertions. Sometimes people expand the word troll to encompass too large a group, but that doesn't necessarily change the definition and I definitely don't see how the article uses it in that manner.
Though, I can definitely understand the desire to expand the definition of the word 'troll' into usefulness. It does make it easier to dismiss other's complaints.