While I agree with most of what you've said, I don't think it's fair to accuse StringingVelvet of trolling. He's bringing up legitimate concerns: If people have bought No Man's Sky here, which I think has at its cheapest been 50% off for $30, it'd be pretty messed up for them to lose access to any future updates (which in the case of this game tend to be pretty significant) because a small, cosmetic part of the game is locked behind a client or internet access when it shouldn't be. The principle behind this is certainly important, and it's something that needs to be fixed, but from a practical standpoint removing the game entirely is a major decision with major consequences either way. If left in its current state, it violates GOG's DRM-free principle which is completely unacceptable. But if removed, countless people who bought the game here get stuck with a dead copy of the game and the chances of them getting refunds are probably nonexistent. Plenty of games have been removed from GOG after treating its customers like second-class citizens or for other reasons, but if there have ever been mass refunds issued in such cases it's been extremely rare.
To me, what needs doing here is simply having the problem be fixed instead of GOG dismissing it. It shouldn't be too difficult to do given that save editors can allegedly already fix the quicksilver store stock issue (proving the content works fine offline as-is) and there's no reason the developers can't simply make quicksilver missions available offline. Even if the daily ones the game currently has are implemented in a way that really won't
work without a client, it would be simple enough to just make quicksilver a possible mission reward in normal missions, including the ones offered on The Anomaly (the space station that offers quicksilver missions and houses the quicksilver store) that do work offline.
Someone asked if quicksilver is completely unobtainable offline, and from what I understand the answer is no. There are supposedly rare events when travelling through space where you can encounter crystals that can contain quicksilver. Of course, this isn't a viable alternative to the missions unless you're okay with spending countless hours drifting through space hoping for RNG to give you the event you want and then getting quicksilver from it. It's also possible to give yourself quicksilver using a save editor, further showing that the currency itself does work offline. Even the quicksilver shop, oddly enough, contains a very limited amount of items when playing offline, it's just that most of the stock is missing for some reason unless you've played online at least once.
I admit that I was a bit harsh in that post, but I was strictly talking about him saying that as long the original content from 1.0 release wasn't taken in any way from you, you shouldn't be arguing about the online only features added through updates; on top of that, he mentioned that it's fine when it comes to MP only portion of the game, while the quicksilver and quests related thing is for 99% SP only, hence my reaction with that post.
All of this was never aimed at delisting the game from GOG (I never mentioned it in the first place).
I also agree with what you said, and that they could easily implement quicksilver currency as normally in game, but it would be even easier to just enable while offline all the content (in short all the online only quests/events and shop items), because there is completely no reason to lock them behind online ESPECIALLY if the game is sold on GOG.
I can be fine with MP modes being locked behind a client or online services, but something that can be played in SP? Hell no.
Years ago there was a similar situation with "the incredible adventures of van helsing final cut" with currency and other content locked as ONLINE ONLY, IN SP TOO, there was an outrage and for a valid reason, and after many complaints the devs decided/were forced to enable them offline too.
I mean, if you (a dev) decide to implement online only content in your game, ok, but at least don't dare to sell your product on a platform which stands against drm and online only stuff, and if you already are, either make workarounds or even better, don't force them as online only.
EDIT: I also want to add that it should be important to note that if people buy games here, is because of GOG DRM free nature, if a game starts as drm free, but then adds non drm-free features, what's the point of selling their games here in the first place?