The provision of pencils in polling booths is a requirement of section 206 of the Commonwealth Electoral ACT 1918 . There is, however nothing to prevent an elector from marking his or her ballot paper with a pen if they so wish. The AEC has found from experience that pencils are the most reliable implements for marking ballot papers. Pencils are practical because they don't run out and the polling staff check and sharpen pencils as necessary throughout election day. Pencils can be stored between elections and they work better in tropical areas. The security of your vote is guaranteed as the storage and counting of ballots is tightly scrutinised.
Your comment about "unenviable record" jogged my memory about events that purportedly occurred not so long ago in the Deep South. If it were historically correct, an expensive poll tax would be included in the story, but that usually is omitted. I'd like to see the entire Bill of Rights walled off permanently from taxation, also known as "the power to destroy." The vote administrators, when faced with a potential black voter, would tell them that a literacy test was required. One particular black gentlemen said "I don't mind a literacy test, I can read and write." Then the chief examiner handed him a copy of a Chinese newspaper asking him to read it aloud. The man looked at it, and said, "No problem, I can read this very clearly." The examiner was stunned. He said "What? You're telling me you can read that?" "Yessir," said the hopeful voter, "that newspaper says 'Ain't no niggers voting today.'" Not so different from what the liars, thieves and murderers do today to trample fundamental human rights.