I'd be interested to know if it was the same people speaking on both occasions though, because it is entirely possible that different sentiments being expressed was a result of different people expressing sentiment, rather than the same people changing their sentiment.

In other words, the same people who disliked TPP before could dislike it today, but not be commenting in the threads talking about Trump's opposition to it and new people who didn't comment on it before could be expressing their opinion formed by recent events (or even harbored from before).

I definitely think an in depth study on internet group think would be interesting, I just think that examining closer to see who composes the group and how it's thinking is an important aspect of that study.