Personally I agree 100% with you in the sense of mental description. A lot of prude, immature, or close minded people will say the only thing that matters with this is anatomy, however they're a dying race. Physically, you are as you were born, and that will never change, you either have XX chromosomes or XY chromosomes. The only exception to this is someone with XXY chromosomes. Mentally however, we are not bound by genders. We are defined by our personalities, not our genetics. Over the internet, nobody is any gender. The only time gender is truly a factor is when that person is displaying their own physical image. If you are truly mentally a girl, then yes, you are a girl online. If you were born a boy, and are mentally a girl, then yes, you are a girl online. If you were born a boy, and are mentally a girl, then no, you are not physically a girl, and never will be.