Every year the wikimedia movement becomes more and more open to users: the current TemplateStiles, the future gadgets' repository. More and more participants are involved in writing code in different languages.
People get together and write one code base; people leave and others have to maintain their code.
And in my opinion, in this situation, a rational decision will be to focus on the creation of a unified code guide for all our projects.
Yes, we have a small guide, but it is for MediaWiki and not everyone knows about it. It seems to me that the best solution would be to make a site like Wikimedia Style Guide. And fill it as Style Guide from Google.