I like this explanation, though there is one form of creative standardization: brand identity. And I suppose that's where graphics folk engage with software (Plasma, the GNOME design, etc.). Amusingly, I like contributing to Wikipedia and the Commons so I should have thought of that. You're absolutely right that I had a blind spot there in terms of what's the equivalent there of free software.
Another thing is that the vast amount of fan fiction out there has a hub-and-spoke model forming an S_n graph around the solitary 'original work' and there are community norms around not 'appropriating' characters and so on, but you're right that community works like the SCP Foundation definitely show that software-like property of remixing of open work.
Anyway, all to say I liked your comment very much but couldn't reply because you seem to have been accidentally hellbanned some short while ago. All of your comments are pretty good, so I reached out to the HN guys and they fixed it up (and confirmed it was a false positive). If you haven't seen people engage with what you're saying, it was a technical issue not a quality issue, so I hope you'll keep posting because this is stuff I like reading on HN. And if you have a blog with an RSS feed or something, it would be cool to see it on your profile.