The graphite dust won't linger long; even in microgravity it's going to end up somewhere due to air circulation, static charge attracting it to something, or a whole host of other mechanisms. It's most likely to end up in an astronaut's lungs or in the air filters. It's not really a problem in either location (your lungs handle worse every day thanks to internal combustion engines and everybody's dead skin) but what is more of a worry is that graphite is a conductor. While dust is unlikely to cause a problem, a whole broken point might be enough to cause a short.
And that's not a good thing to have in an environment dependent on technology...
(That'll teach me to check that I'm actually logged in before posting...)
Because gravity is still in action on the ink when the pen is horizontal, at a guess. Writing with the pen held horizontally isn't the same as writing in microgravity - in microgravity the stickiness of the ink is more than capable of pulling more ink towards the ball as it writes, whereas with the pen held horizontally in normal G it still has to pull ink "uphill" against gravity towards the top of the ball.
It'a another example of how nearly impossible it is to extrapolate what happens in space or on the Moon from our experiences on Earth - for more examples, check out Bad Astronomy on the Apollo "Hoax"
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And that's not a good thing to have in an environment dependent on technology...
Because gravity is still in action on the ink when the pen is horizontal, at a guess. Writing with the pen held horizontally isn't the same as writing in microgravity - in microgravity the stickiness of the ink is more than capable of pulling more ink towards the ball as it writes, whereas with the pen held horizontally in normal G it still has to pull ink "uphill" against gravity towards the top of the ball.
It'a another example of how nearly impossible it is to extrapolate what happens in space or on the Moon from our experiences on Earth - for more examples, check out Bad Astronomy on the Apollo "Hoax"