Achievements! Achievements! Achievements! *rolls eyes until they fall out of their sockets* ... And the broken records go round and round, round and round.
Are you meaning to imply that GOG customers shouldn't
complain about being treated like second-class citizens via receiving featured-removed version of games that have Achievements on Steam...even though GOG customers' hard-earned money which they shell out for their games is 100% as real & valid as Steam customers' money?
Because that implication that we shouldn't complain about this matter would be incorrect.
We should indeed keep complaining about that, and demand full equal rights & treatment, until such time as equal rights & treatment have been fully achieved.
The "broken records" can stop when devs start being honorable,and stop shafting GOG customers in this regard. Once that happens, then the devs who haven't been giving their GOG versions feature parity with Steam would be giving us nothing to complain about in regards to this point, hence we wouldn't
complain about it once they have decided to treat us fairly.
As for the "who's to say they won't add Achievements?" question... better question is: who's to say they will?
It's possible they might add Achievements at the last minute, as happens with a few GOG games, but usually, for the most part
, when Achievements aren't listed on the GOG store page at the start, then they never
come later either.
So, best practice is to presume they won't ever be coming, until they actually do, and/or until the devs explicitly promise that they will be coming (neither of which has happened in the case of Coma 2, AFAIK).
Given that Coma 2 has Steam Achievements as proven by the Steam store page for it, then I will be not buying this game at all (neither on Steam, nor on GOG, nor anywhere else) if it doesn't have Galaxy Achievements. But I will buy if it does. I'm sure there are other GOG customers who also feel the same way.