It's unlucky to write with a broken pencil.
Never wish a writer good luck. Say: Have a funny punch-in-the-face line.
It's bad luck to close your eyes when you're writing.
Writers' Superstitions
Are these jokes or actual superstitions of yours?
It's bad luck to ask.
Is it?
>_<
It's bad luck to put emoticons on a thread about writing superstitions.
It's bad luck to make weird threads.
It's bad luck to be superstitious.
It's good luck to be superstitious. 
In a logical universe, there is no 'luck'.
Although I doubt the poster was being serious, everyone knows writers are infamously superstitious. There have been some real nutcases, Romantic poets probably being the worst offenders. Coleridge, Shelley, Wordsworth, Byron, all had weird superstitions about when to write, how to write, what colour ink to use, even how many syllables to use in a line. Green ink was actually favoured by poets, but wearing green wasn't while writing. Wearing white was always favoured as it symbolised the virgin page ready to be filled up. Spilling ink was a bad omen, and washing ink from your hands was always to be avoided until the poem was finished. Food was rarely favoured while writing, and it was very bad luck for others to see your unfinished work or for your page to fall to the ground ink side down. Clocks were never allowed in the room while writing, either. Some animals were said to be lucky as company, cats were always welcome.
Kittieees!
All writers should have a cat.
Its bad luck to have bad luck.