He refused to wear a General’s rank on his uniform
Lee had been offered a senior rank in the Union Army prior to Virginia seceding, but once it had he accepted the rank of Major General of Virginia Militia. In May of 1861, this rank was superseded by his commission into the Confederate States Army as a Brigadier General.
One month later he was promoted to the rank of General in June 1861, which he held through most of the war. In January 1865 he was promoted to the rank of General-in-Chief of the Confederate Armies.
The highest rank Lee had achieved in the United States Army before the Civil War was that of Colonel of the First Regiment of Cavalry, awarded him in March 1861. Lee chose to retain the rank insignia of a Colonel on his Confederate uniform. He informed friends privately that he would not wear the insignia of a Confederate General until such time that the war was won and the Confederate States recognized as an independent nation.
Despite this quirk, Lee was punctilious about his appearance and military bearing at all times. He strictly adhered to military address with his subordinates, always referring to them by their rank or with the honorific “Mister” to junior officers. He did not use familiarities with his senior officers, many of whom he had known since boyhood, and many of whom he had served with in various military posts as younger men.
Of all his generals, only one – Henry Heth – would he address by his Christian name. Despite his own refusal to wear the badges of his rank he demanded strict adherence to uniform standards by his senior officers, even as the troops under their command became more and more bedraggled as the war went on.