This has been asked before: Why doesn't Visual Studio code formatting work properly for Razor markup?
But that question is a couple years old. And Razor formatti
The places to look:
Tools -> Options -> Web Essentials -> HTML -> Auto-format HTML on Enter
(Requires installation of Web Essentials extension)
Set to False
Tools -> Options -> Text Editor -> HTML -> Advanced -> Format on Paste
Set to False
With these settings I have no trouble in Visual Studio 2013.
I used to have to press Ctrl-Z far too often, and if you forgot untangling the mess once your code was written and tested was a huge pain. I feel Microsoft could do alot to help users configure this as well as make it more accessible.