Quill provides greater flexibility than a brush.
It was much later, in the 1600s, with the increased popularity of writing, especially in the copperplate script promoted by the many printed manuals available from the 'Writing Masters', that quills became more pointed and flexible
 Additionally, writing with the left hand in the era in which the quill was popular was discouraged, and quills were never sold as left- and right-handed, only by their size and species

