For several reasons during development I sometimes comment out code. As I am chaotic and sometimes in a hurry, some of these make it to source control. I also use comments to clarify blocks of code. For instance:MyClass MyFunction(){    (...)    // return null; // TODO: dummy for now    return obj;}Even though it works and alot of people do it this way, it annoys me that you cannot automatically distinguish commented-out code from real comments that clarify code:it adds noise when trying to read codeyou cannot search for commented-out code for for instance an on-commit hook in source control.Some languages support multiple single-line comment styles - for instance in PHP you can either use // or # for a single-line comment - and developers can agree on using one of these for commented-out code:# return null; // TODO: dummy for nowreturn obj;Other languages - like C# which I am using today - have one style for single-line comments (right? I wish I was wrong). I have also seen examples of commenting-out code using compiler directives, which is great for large blocks of code, but a bit overkill for single lines as two new lines are required for the directive:#if compile_commented_out    return null; // TODO: dummy for now#endifreturn obj;So as commenting-out code happens in every(?) language, shouldn't disabled code get its own syntax in language specifications? Are the pro's (separation of comments / disabled code, editors / source control acting on them) good enough and the cons (shouldn't do commenting-out anyway, not a functional part of a language, potential IDE lag (thanks Thomas)) worth sacrificing?EditI realise the example I used is silly; the dummy code could easily be removed as it is replaced by the actual code. 
Should the syntax for disabling code differ from that of normal comments?
comments;syntax
First of all, in your example there are TODO comments. These types of comments are special in a way because they are detected by IDEs (at least Eclipse and Visual Studio) as a marker for tasks. But I'm sure you know that since you use thme, and I suppose you're not referring to them when you use the term disabled code.As for the disabled code itself, my opinion is that it pollutes the code. I use another mechanism to keep track of what was there before: the source repository. Except when I'm in a code/test/code/test... mode, I don't comment unused code, I remove it. And when it's the case commenting X lines is just a matter of one keyboard shortcut. Edit: so yeah, I forgot to answer your explicit question, I think that it's not useful to have special comments for disabled code. If you really want to keep the code, but say don't use it, you can always mark it as @deprecated but that was not the point of your question.