So, in this case the character he used was rare because it was obsolete.
Would Packard have know that if, in fact, he actually knew what the word meant and wasn't reading out of a dictionary?
Obviously, but there is a difference between obsolete language and ceremonial / official language. It would be like saying a lot of the words used in English for jurisprudence would be rare in common language.
The part about you getting into an argument about stroke order. Which, by the way, is very important unless you're a stupid weep writing one character for a message board instead of, you know, using the character to communicate.