On September 19, Ruby Central, a nonprofit organization that manages RubyGems.org, a platform for sharing Ruby code and libraries, asserted control over several GitHub repositories for Ruby Gems as well as other critical Ruby open source projects that the rest of the Ruby development community relies on.
Uhm, so how does this happen? If some people create Ruby Gems and host them under their own github account, how would Ruby Central suddenly assert control over them?

This sounds similar to "Static code analysis" tools. Especially now that these code analysis tools are getting AI integrations.
For example we use coderabbit.ai. That does a code review on PRs in github, and reviews these sort of things. Especially the simpler things that you've mentioned like poor naming conventions, violations of language-specific best practices, and readability issues. I'm not sure if it will automatically come up with "large refactoring opportunities" by default - but maybe you can custom-prompt configure it to try, I guess
Coderabbit also has IDE extensions: https://www.coderabbit.ai/ide - I think the separate webpage exists for org level configurations and overviews. These "best practices" are probably defined on a team level to ensure everyone uses the same code-style and things like that
I'm not sure if "just a website to copypaste code and get reviews" is really a good idea. Maybe for juniors that want to review one class or method or something. But usually code is spread across multiple files, and structural refactor opportunities are on a larger scale then just a couple files