Sutter, Jokinen(many times), Richards, Carter, Kesler, Ansimov, Dubinsky, Brassard, Ryan O'Riely, Jordan Staal etc etc. The second and third tier centers move all the time
It's the superstars and franchise players(like a 100+ point Joe Thornton as per your example) that never move. RNH doesn't qualify as either.
Sutter was considered a clear 3rd line center when he was dealt to the Canucks and when he was dealt to the Pens it was because Staal wasn't going to resign, or in other words forced a trade. Also nowhere near Hopkins in ability.
Jokinen was considered a problem child that didn't use his teammates, but he's not a bad example. However in hindsight Florida lost that deal.
Richards was on the down swing and Philly made an astute move to move him, and plus there were the rumours about his lifestyle that seem to have been true knowing what we know now.
Carter was a huge mistake and i'm sure they still regret it.
Kesler forced a trade.
Anisimov was their 3rd line center or playing wing at the time, no where near comparable to Hopkins. He was also traded for a much better player.
Dubinsky like Anisimov was traded for a much better player.
Brassard was being healthy scratched and considered a near bust. Columbus felt they were upgrading by getting Anisimov-Dubinsky.
O'Reilly forced a trade by essentially making it obvious he wouldn't resign.
Staal as i said above wasn't going to resign.
Most of the deals you stated were for players who at the time were no where near Hopkins in ability, had personal issues, were traded for an upgrade, forced a deal or were going UFA, or were regrettable deals in hindsight. So in summary the poster you quoted was correct.