What language prevents TIMTOWTDI? And don't say Python. I'm not talking about the language motto. Because that's the nature of using these things called programming languages: http://www.paulgraham.com/langdes.html

Python has Pep8. Perl has Perl::Critic. C# has FxCop. Etc.

I've not yet seen any language possess the qualities that prevent it from being unreadable. It's an amazing open question though, isn't it?

I think you hit the point with "code maintenance can become a huge headache due to someone not understanding the idioms used by the person who originally wrote the code". But this isn't a language thing. This is a people thing.