That's great for you while you're editing. But your code is still going to display with horizontal scrollbars for other users who don't hide the right panel (which can actually be quite useful). Even worse, you should see the effect this has on an iPad - you have to scroll to see all the code but there is no visual cue that you have to do so (no scrollbars).
What I would like to see much better is an effort to make code presentable without horizontal scrolling. Every language I know of has the ability to break up a line of code, a string, an expression, what have you and continue it on the next line. While it's a little more work, it's a solution that helps everyone, not just the author of the code.
If I go through my edit history, I bet I will find at least a few hundred edits that, among other things, eliminated horizontal scrollbars from a code sample by removing unnecessary white space and introducing line continuations. If I can do that for other users' questions, surely the author of the question can make some effort as well, especially when they are fully aware of the problem.