DEAR MISS MANNERS: I was active-duty military, eligible to shop in the commissary, where goods were somewhat less expensive than at a civilian market. My pay was also less than the equivalent civilian profession.

A civilian mom who lived upstairs from me once sent her child to ask me for a can of tuna. I supplied them with a can of albacore tuna from a common brand. A few days later, she replaced it with an equal-size can from the same brand, but of lesser quality tuna. The price tag on her can was within a few cents of what I paid for the albacore.

Her action was deliberate. Never again.

GENTLE READER: Your certainty that there was a snub in repaying your kindness with inferior tuna perplexes Miss Manners. Perhaps there is a backstory -- or direct evidence -- you neglected to mention.

But if you are instead just following the newly popular trend of reading ill will into a casual act, are you not being both unkind and illogical? These days, when people seem eager to scream obscenities at passing strangers, who can believe that anyone would take the trouble to be so subtle with an insult?

DEAR MISS MANNERS: My wife and I are close friends with another couple. We have traveled locally, domestically and internationally with them. We have been on countless outings, and are closer to them than we are to our own families, save our parents.

They are among our truest, dearest friends. Our relationship with them means a great deal to us both, and we cannot imagine not having them as part of our social lives.

We have been informed that the recently engaged sibling of one of them intends to invite us to their wedding. I find this odd. Over the past decade-plus, the number of occasions that we have been around this sibling can be counted on one hand. We have never received any invitations from this person in the past, we have had very few direct interactions with them, and we've never even met the spouse-to-be.

Given the increasing prevalence of gift-grabbing in the guise of group gatherings, I cannot help but think that that is the motivation for including us. I have no interest in attending this wedding, nor in providing a gift.

What is your recommendation for declining an invitation from the sibling of a very dear (and very sensitive) friend? Or should I bite the bullet for the sake of this long-term friendship and spend a day with gritted teeth? Am I obligated to give a gift either way?

GENTLE READER: My goodness. Miss Manners would have thought they told you to walk the plank rather than invite you to their wedding.

If you hate the idea of attending that much, politely decline. But would it not be better for everyone if you assume that the sibling of your dearest friends invited you because they consider you family -- and not as a gift grab?

(Please send your questions to Miss Manners at her website, www.missmanners.com; to her email, dearmissmanners@gmail.com; or through postal mail to Miss Manners, Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106.)

DEAR MISS MANNERS: What is the proper response when a casual acquaintance tells you that they have been diagnosed with a very serious illness?

This is a person I have no connection to or interest in getting to know better. We merely pass each other in our building while picking up the mail or going to the parking lot.

My reply, as I was rushing to a dental appointment, was, “I’m sorry to hear that. Hope things work out for you.”

What more was I expected to do or say?

GENTLE READER: Nothing. That’s about it for a casual acquaintance. Many people seem to be unable to stop speaking, however, and there are many things you shouldn’t say:

“My uncle Larry had the same thing and he lived to be 90.”

“I’m in bad shape, too; it’s my knee.”

“It’s a matter of positive thinking.”

“Do you trust your doctor?”

“I guess we all have to go sometime.”

“Have you tried changing your diet?”

And so on. The point is to offer sympathy -- because unfortunately, you have nothing else to offer.

DEAR MISS MANNERS: My neighbor and I had a heated disagreement about trick-or-treating.

We are fortunate to live in a picturesque neighborhood of single-family houses, and our street is popular every Oct. 31. We often get trick-or-treaters from other areas.

Although I like having lots of kids to give treats to, my neighbor says this year, she is refusing to give candy to any “outsiders.” She says these children and their parents are “mooching.”

She actually hopes to get the neighborhood association to ban outsiders that night. At the very least, she will ask each child’s parents to prove they live in the neighborhood.

I think this is ludicrous and against the whole spirit of the carefree holiday. She says she is just correcting poor upbringing. Is she?

GENTLE READER: More like demonstrating it.

Miss Manners is guessing that these children are in your neighborhood because it is safer than theirs -- in terms of foot traffic, at least. But apparently not in terms of kindness.

DEAR MISS MANNERS: Too often, waiters interrupt conversations between restaurant customers. While I understand that restaurants are not the place to have private or intimate discussions, it is still extremely annoying to be cut off midsentence by questions from waiters that are hardly ever important.

I have tried ignoring them by continuing speaking or listening to my dinner companion to no avail; the waiters just come closer and repeat their intrusive questions. What response or behavior do you suggest in such instances?

GENTLE READER: With all due acknowledgment of the burdens placed on harried waitstaff, this should not be done. Miss Manners suggests the universal signal of wait-a-minute, which is to hold up a finger, flash a quick smile and go on talking.

DEAR MISS MANNERS: My son and his fiancee are insisting that my other son, as a groomsman, shave his mustache. They do not like the way it looks. Is this out of line? My groomsman son is highly offended.

GENTLE READER: Of course he is. It is highly offensive to be told that you are not acceptable as you are.

(Please send your questions to Miss Manners at her website, www.missmanners.com; to her email, dearmissmanners@gmail.com; or through postal mail to Miss Manners, Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106.)

DEAR MISS MANNERS: Is it appropriate for my daughter-in-law to say to me, “Why don’t you ask us what we want, rather than just getting something that we may not want or use?”

I was offended, because I thought gift-giving was the giver’s choice. Otherwise, it feels like the recipient is just placing their order with me. Offensive!

GENTLE READER: It is very offensive, but allow Miss Manners to explain where it is coming from.

Some time ago, the ancient custom of exchanging presents took an unpleasant turn. “It’s the thought that counts” became a joke to those who wanted to do away with the donor’s thoughts and get what they chose themselves. And many prospective donors agreed that it was too much bother to have to think about what might please a recipient.

Hence the spread of the gift registry and the end of the thoughtfulness element, which had been the whole point of giving presents: “I know you, and I am guessing that this will please you.” This method could go wrong, but gave great pleasure to both donor and recipient when it went right.

Your daughter-in-law takes the popular view that giving presents means exchanging shopping lists. No fun, no pleasant surprises (but also no unpleasant surprises) -- and no finding out that someone close to you really understands and appreciates you.

You should discuss these different approaches with your daughter-in-law, and probably also your son, and decide if either of you want to switch systems. Or perhaps you could compromise: For example, they might tell you what category of things they like, or call attention to their taste.

Question: How do they choose their presents to you?

DEAR MISS MANNERS: When hosting a sit-down meal, which is more correct: to clear away plates as each diner finishes a course, or to wait until all have finished eating before clearing the table?

The first option seems to send a pointed "hurry up" message to the last person to finish; the second can leave speedier eaters staring for ages at their own dirty plates. Counsel, please!

GENTLE READER: The best counsel Miss Manners has for you is to invite guests who engage in conversation, so that they are not left staring at their empty plates when they have finished eating. Courses are properly cleared when everyone has finished.

DEAR MISS MANNERS: If I bring a food item that I prepared, and it turns out that someone else brought a similar item, is it impolite for the host to say, “You shouldn’t have brought this. I already have some”?

Or if I bring something and then when I'm leaving, the host says, "Take this home; no one will eat it"?

GENTLE READER: Wow, you have a mean crowd. You cook for them, and they insult you for your efforts.

The first problem would be solved if your group appointed an organizer to assign contributions. The second could be solved with a modicum of tact: “Sorry, we didn’t get to this, and I don’t have room for it.”

(Please send your questions to Miss Manners at her website, www.missmanners.com; to her email, dearmissmanners@gmail.com; or through postal mail to Miss Manners, Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106.)