I haven't figured out how to get it to work in Visual Studio 2017 either. I've looked in the VS settings and Resharper settings (for those that also have that), with no luck.
However, if you open the file in VS Code (or sublime text, or atom, or pretty much anything else), comments work exactly the way you're looking for. It's a poor workaround to need a second app for editing files, but it was the best I could find.
And for the guy who dismissed the issue, the block quote format (/* ... */) breaks if the section you are quoting already has a block quote (or more than one) in it. Then you're left manually commenting out a ton of blocks that you can't easily uncomment. I hope microsoft changes this behavior in the future, as it hampers the ability to use sass files in the paid version of VS (but not VS Code!).