Hi Jakob,
thank you for reaching out! You got some answers for the demonyms.
Regarding how to best learn from this for the Abstract Wikipedia: as you say yourself, the code itself is just a few lines - but they come with a lot of interesting lessons attached to it.
As you start doing that for an increasing number of languages we will run into interesting issues, such as differences by grammatical gender being expressed in some but not in other languages, how to deal with historical countries, how to deal with cases as Marie Curie, Tesla, etc.
I think capturing these in an essay either on your web site or on wiki can be very valuable.
Again, I think the code itself will be short and can be quickly rewritten - but the lessons you learned on the way will too easily be forgotten if not captured.
Thank you,
Denny