Is one who says, "I like writing with my left hand," sinful, knowing the Messenger, may Allah bless him and grant him peace, preferred using the right, and is his statement considered contrary to the Sunnah? What is incumbent upon him if he loves to repeat that?

Writing with a pen is a great blessing and a means of education. It is an honor for the writer and is among the things for which starting with the right is commendable, as it falls under the category of honoring and dignifying. The original principle is that it should be with the right hand for whoever is able to do so. However, if writing is done with the left hand due to an inability to write with the right, then there is no harm in that.