In How do you handle parameters & blocks when dynamically defining a method in Ruby? , code is being indented four spaces rather than the idiomatic two spaces, because the OP is using tabs.
If markdown treated tabs as being two spaces rather than four, then it would look idiomatic.
I assume this could be handled either based on markdown's automatic detection of programming lanuage, or the tags used.
If someone really likes four spaces per indentation level, then they can do so by manually using four spaces.