I always thought the list was real. I really don't see why some would doubt it.
I'll reserve judgment until a confirmation shows up, but I'm convinced this is the real deal.
I doubted it when there was little to no information to indicate whether it was true or not.
I doubt it now when people take a word/situation from the achievements and somehow try to link it to new tidbits of information. The chief offender for me would be the whole Capital Occasion and the "Solve a problem with the Chantry in Val Royeuax" war table mission.
If the mission specifically stated the "problem" was what the achievement details then I would see no problem with it, but since it doesn't it would seem to indicate that there is some other way to get that achievement that is not related to that mission. Perhaps the problem we are solving is a result of the achievement, but I doubt it unlocks the achievement.
As for the evidence that supports the achievements (the rune comes to mind) I am not going to argue because there are no alternate explanations for it. If there were, I would be posting incessantly about it while liking annoying numerous people when I point out their use of confirmation bias.
It's a long bow to draw to think that someone was smart enough to associate the Inquisitor looking at the night sky with astronomy and astrariums, *and then* want to troll everybody enough to make fifty separate fake achievements.
The only thing I will point out here is, do we know if astraiums exist in Thedas?
As for faking the achievements, I would not be surprised.
You may laugh and insult me for that belief, but my skepticism has never led me into a situation I regret.