Sirius Black has immaculate handwriting. He can do the most gorgeous, fluid joined writing, even though he prefers not to join. Not that anybody knows this because as a left handed person in a world that uses very wet ink, everything Sirius’ writes falls somewhere on the ‘it’s a bit messy’ to ‘did you finger paint with the ink’ scale.
It drives whoever has to sit next to him crazy because his friends are all righty’s and therefore have to compete for elbow room when they’re writing, which is bad enough as it is without taking into account that Sirius likes to write sprawled out with both elbows on the table. He has a permanent ink stain smudged on to the edge of his left hand because of this and manages to leave inky smears on everything he touches during the day when the ink never fully has chance to dry.
He’s also a quill chewer. If he has one in his hand then the other end is almost definitely in his mouth or he’s brushing it absently across his lips, which he always does unconsciously. It drives Remus up the wall because ‘it’s come from a bird Sirius. A live animal, for the hundredth time take it out of your gob’.
Remus’ handwriting has two forms, slow and neat or rushed and horrendously messy. When he takes his time, such as when he’s doing his homework, he writes really small and tidily, but in class he just jots down everything he can and it’s virtually unreadable.