Tabs are currently rendered as spaces in code blocks. I'm sure this is just a symptom of Markdown or an otherwise well-intentioned method to standardise code samples... However some code needs tabs to work.
<<- EOF ... EOF heredoc in Bash. The dash means it will skip a number of leading tab characters. Not spaces. So when you advertise this feature (it makes code much more readable) and use it on the site, it breaks. The heredoc output is littered with leading spaces.
The example I used above is from Unix.SE. I believe this is as much an issue for them, just as it might be for any Bash-tagged question further afield.