The problem actually is weightlessness, not vacuum. Normal ballpoint pens rely on gravity to pull the ink down against the ball, so it can get rolled onto the paper. Fischer space pens have pressurized cartridges so they work without gravity (or even against it--they can write upside down here on Earth).
He agrees with you. The quote in the article cites vacuum as the reason.
Whoops you're right. I misread! Sorry.
Normal ballpoint pens do not need gravity, they just need gravity not working against it. Normal ball point pens work in space. The space pen is probably more durable for other reasons.
You know, if you're trapped outside the space craft and left to die, the last message you ever write could be graffiti written in a vacuum on some passing object. You want a pen that can write in a vacuum. Now, I'm sure you're saying, perhaps the pen could come with a microburst of thrust instead, to save said astronaut. Now you're just being silly.