I mean clickable hyperlinks in its games description boxes, similar to those links you can create in the GOG forums.

Also, a question about GOGmix ratings: Are they connected to the ratings you post in each game's gamecard? Is it possible to have two different (GOGmix rating / gamecard rating) ratings for a GOG?

By using the same syntax manually?

It doesn't seem possible to use links, the forum syntax doesn't work at least.

Forum syntax and HTML syntax don't work, so I'm pretty sure it's not possible.

That’s a pity!

Is this by design or just a bug waiting to be fixed?

I'm pretty sure they built the entire site themselves (instead of for example using PHPBB for the forums etc), so it's probably just an oversight.
Either they never thought somebody would want to do that, or they're worried where those links might lead. But probably, they never thought anyone would use a function like that.
You could contact their support/webdesign division and ask them to code that in, shouldn't take them more than an hour or so (if they decide to do it).

What about the ratings? Are they always connected?

By the way, is it normal for every GOGmix to be displayed with the same background picture?

I think background pictures used to vary according to the first game listed each time.

Since no other thoughts are being added, I am marking this topic closed.