Oh my god,The comment button in Visual Studio 2012/2013 tool bar is missing!
By default, Visual Studio 2012/2013/2015 does not add these options [Text Editor] automatically,
To show the Comment / Uncomment buttons you should add the Text Editor options by following the bit steps below:
Click right on free space in tool bar then select Text Editor
The following buttons was added to tool bar !
In Visual Studio 2008 / 2010, the comment icons should be look like the following shapes