Showing one controller action or model method will not compromise your application security.

I'm not saying people should put their application to github, just asking them to use real examples in their articles (like I did with MessagesController#create)

In security circles Kerckhoff's principle is usually accepted. (https://en.wikipedia.org/wiki/Kerckhoffss_principle) It essentially says, that security by obscurity is a bad idea.

I wouldn't be. Some of the most secure software in the world is fully open source. Having millions of eyeballs looking and touching your code is a lot more secure than having 5 ego-driven devs who think they know security.