It's been on sale here for months....

Welcome! You'd be surprised how many games are missing message boards. There's what, nearly 2500 games? Well, there's only 2378 forums.

Many of which have never seen a single post, but that's aside the point.

Don't forget that of >3000 items available in the shop a great number of them consists of DLC, albums, artwork, season passes, standard, deluxe, directors cut editions and upgrades. Talisman DLC alone account for at least up to 25 items! So the number of games without dedicated boards should be quite low and those who got them are mostly empty ... Be it because developers just don't care wasting time here instead of Steam or whatever. When one is missing it could be a case oversight, that, when brought to GOG's attention they will add it. In re OP, this last sentence. ;-)

Even GOG's sheer abject aversion to grouping properties, the fact remains that there are a number of games that have been here for years and persistently lead back to the main forums than their dedicated forum.

True which goes into what you are complaining about which is lack of grouping. 9 times out of 10 this happens when you don't select a standard version will you be re-directed to the Community Discussion board. This also affects browsing reviews which I made a suggestion 2 years ago which went unheard by GOG. It is possible to write a review for deluxe edition and standard edition of a game but you must select either version to be able to read those reviews. Tagging them to know which version was reviewed and having one single page for all editions, sort of when selecting deluxe, you aren't transferred to a dedicated website but the shop page expands telling you what it contains. Lastly if GOG were to mark a standard version as owned in case you buy a 'better' version - for lack of a better term for it, it would also make it easier to browse the shop page. Same with merging a standard and deluxe version and only leave the 'best' version up for download in your library. This would also save time for GOG to maintain it all and in the long run also money saving traffic and server space both on the website as maybe in Galaxy also. Moot to even mention this as it will go unheard and telling you is preaching to the choir since that's something you already know and likely agree to.

People also may want to discuss the games, have issues, etc. Games without a message board have no area to discuss the games in question. It may impact sales as well...