A person who writes commentaries is typically called a commentator or a critic. They provide analysis, interpretation, and opinions on various subjects such as literature, art, or current events.
A person who writes a will is commonly referred to as the "testator."
A Philosopher
A person who writes the libretto for an opera is simply referred to as the librettist.
A drawer.
proposal
A poetry
publisher
A person who writes verses is a poet.
Columnist
Author
Reporter
A columnist...?