The HBO hit show came to an end in May, after first airing in April 2011 and growing into a global phenomenon.
But as the last season drew to a close this summer, some viewers were so dissatisfied with the episodes that they signed a petition calling for the eighth and final series to be rewritten and reshot in order to deliver an alternative ending.
And now, 48-year-old Coster-Waldau - who portrayed Jaime Lannister for 8 years - has said the "vicious" comments hit certain members of the cast very hard.
“Every season has been intense in terms of the attention and discussion, but it was extraordinarily intense for a final season,’ he said, according to HuffPost.
He added: “And we have this WhatsApp group, the actors, and I saw some people getting a little upset because some of the stuff is vicious, and if you make the mistake of start reading all that s***, because if you guys get really angry about something - I'm sure you did, some of you - so you write to each other and go, 'F***ing a**holes. This is so not what would happen! They ruined, they butchered George's world!'
“It's just fun for you, but of course some got a little upset."
The Danish-born actor continued: ‘There was that weird feeling of, “What the hell? We worked so hard.” I’m not asking anyone to feel sorry, by the way. That’s not what I’m saying. I’m just saying how it was to get through that whole thing.’
In short, the Kingslayer just wants fans to take it easy on his friends.
Meanwhile reports of the Game of Thrones prequel being filmed has been exciting some viewers.
Reports in The Belfast Telegraph suggest that the cameras are rolling in Northern Ireland on one of the new prequel series, which is set around 5,000 years before the main show.
The publication claims that filming started in June for the as-yet-untitled show in County Down, with various locations also being set up across Belfast.
They are thought to include Tollymore Forest, which originally appeared as Winterfell, Inch Abbey – Rob Stark’s base camp – and The Dark Hedges.
Plot details for the prequel, which will star Naomi Watts and Josh Whitehouse, are being kept tightly under wraps.
The official description says that the series will “chronicle the world’s descent from the golden Age of Heroes into its darkest hour”, unravelling and retelling the “story we think we know”.
It continues: “From the horrifying secrets of Westeros’ history to the true origin of the white walkers, the mysteries of the East, to the Starks of legend… it’s not the story we think we know.”
And Game of Thrones author George R.R Martin pointed out to Entertainment Weekly that he has written “very little” about the period during which the prequel is set, meaning director Jane Goldman could pretty much go anywhere with it.
“There’s no King’s Landing. There’s no Iron Throne. There are no Targaryens,” he told EW. “Valyria has hardly begun to rise yet with its dragons and the great empire that it built.
“We’re dealing with a different and older world and hopefully that will be part of the fun of the series.”