Twice I have been to graduation ceremonies where the same principal has used the word "commence" to mean "end" rather than "begin." I would like to write to him and tell him that although logic is on his side and I have always thought that a more appropriate word could be used at graduations, he has embarrassed himself in front of those who expect more from a man of his position.
My question: should I bother? Will it make a difference? And how often have you heard someone who should know better misuse a word in a situation where it is an affront?

Well, to me the idea behind "commencement" is that the ritual signifies the beginning of young peoples' adult lives; one of the modern-day rites of passage.

I would definitely correct the principal -- if I didn't still have any kids at that school!

The ceremony is commenced? Let it slide. But if he asks you to write a paper on the Emasculation Proclamation, then reach for your snootiest writing paper and your biggest dictionary!

I think it has to depend, as AnnaStrophic has inferred, on what relationship you have and what you wish to have, with this man. I once worked for a man I respect greatly, even years after he left. The one thing that nearly gave me brain bleeds was when, in meetings with colleagues, parents, "underlings" and so on, he would say, consistently, things such as "I have a pacific idea in mind." I could not bring myself to correct him, even anonymously, and I never will, even though he is no longer my boss and I have "nothing to lose". It just seems the wrong thing to me. Perhaps it is because I imagine it would be a greater to hurt to him than him going through life misusing the word. It didn't affect my respect for him (although I didn't like it!), so I imagine most others forgave it, also. :0)

The dictionaries mostly seem to say that an affront is deliberate or intentional so don't rush into anything lest you be awarded the Pullet Surprise yourself.