DEAR MISS MANNERS: I believe you have said that it is rude to show up at someone's house with your own recently purchased coffee drink. I'm wondering why this practice is considered inappropriate.
My guess is that it insults the host by implying that nothing he or she could offer would please the guest as much as the tall organic half-caf extra-hot nonfat vanilla soy latte with extra foam. I am wondering why it doesn't suggest to the host, "Don't worry about me; I've taken care of my needs so that you can relax."
GENTLE READER: You are asking Miss Manners to put aside the argument that universally and throughout recorded time, refusing hospitality has been considered a serious insult. Diplomats and travelers have, for that reason, choked down all kinds of foods and drink that they found unpalatable, not to mention disgusting.
But that still leaves her with a strictly practical argument, which applies not only to the visitor with the coffee cup, but also to the guest who brings a bottle or dish when invited to dinner and expects it to be served. That is that it does not, in fact, save the host any trouble.
On the contrary, if the guest was expected for a meal, the host would have had to prepare it in advance anyway, and serving the extra food (setting it out, replacing what was planned) or drink (which may not go with the food and in any case is not likely to be enough to go around) may be extra trouble.
The casual visitor who strides in with his own coffee is not only usurping the function of the host (oops, Miss Manners was going to sidestep that point), but doing so, ungraciously, only for himself. If the host wants some, he still has to make it.
DEAR MISS MANNERS: I have been promoted to supervisor over a department of seven employees. I am much younger than the staff that I supervise, and I possess more credentials.
Two out of seven find it necessary to comment on how I dress or my shoes or my hair, usually in a negative manner. I smile and brush it off because I know in my heart what the real issue is, and I also try to deflect their attention. I know how to be rude and insulting, but I'd rather remain tactful and professional and yet get my point across.
GENTLE READER: But you are the supervisor, so you can require that they also behave professionally.
You will do better if you generalize the problem to avoid even more personal remarks about your being "oversensitive" or "unable to take a compliment."
Miss Manners recommends an office-wide memo stating that of course everyone knows that modern professional conduct prohibits making personal remarks about colleagues, and you would like to remind them that this includes compliments. That will throw them off your trail because they were not exactly giving you compliments.
Then the next time someone begins to criticize you (or even, inspired by your remark, offer you a compliment), you can issue a gentle reminder about professional behavior, thus also reminding them that you are the supervisor, whom it is unwise to antagonize.