I have no idea if this is the right community for this question, so please feel free to move it if it is not.
In Visual Studio 2015, there appear to be six character spa
First: Tools > Options > Text Editor > C# (or whatever language you use) > General > untick "Line numbers"
Second: Tools > Options > Text Editor > General > untick "selection margin" and "indicator margin"
If you are meaning this gutter between the line numbers and the gutter for break points, it how is used to display various code helpers (e.g. refactor indicators, lightbulbs for code improvements etc.)
If you take those indicators away you have about 2 extra character spaces.
There are following margins left of code: breakpoints/bookmarks (17 px), line numbers (35 px), quick actions (18 px), file changes (10 px) and outlining (9 px).
I don't see any deliberately wasted space and I don't see any public options to change width of existing elements.