Bagoas, you have raised some very good points here. To address some of the points raised by others. 5 or 6 commented lines using "//" won't make any noticable diffrence to the loading time of a typical file. Using a material name for a comment:

   material This is a comment 
                {
                }

If the comment exceeds (I think it's) 32 characters including spaces, it will be truncated on a resave. Upon a resave poser will add some paramiters to the material block.