Why shouldn't girls be able to use their real avatar? If a someone doesn't want someone else to creep on them, and asks for the offending party not to, that person should respect that. It's the fault of the person creeping for being disrespectful, not the fault of the person with the 'real avatar' for deciding to put their face on the internet. That's like saying that someone deserves to be harassed for having a face that others deem attractive.
On that note, I fully support the block function. Hope it gets implemented soon!