DEAR MISS MANNERS: I am usually good about thanking people. Now, I am flummoxed. A note or even a gift seems so inadequate for what friends have done for us.

In one case, some friends hosted my husband when he was cleaning out his mother's house, hours from home. They looked after the mail and even took my mother-in-law to get a COVID vaccination, which took them hours! The friends wouldn't even take my husband up on his offer to take them out for a meal in return.

Another friend did some professional work for us that I offered to pay for, but was told he doesn't work that way. (Years later, when we tried to continue the work, we were told he can't help us, so there may be bad feelings there.)

What do you suggest we do to thank these people who we cannot possibly thank enough?

GENTLE READER: Not thanking someone when no thanks will be enough is a natural reaction -- and one to be avoided at all costs. You may feel overwhelmed by their generosity, but from their point of view, you did not even care enough to acknowledge it.

Tell your friends the truth: that you were overwhelmed by their generosity at the time and cannot ever forget it. And that you feel terrible at having neglected to insist on paying for that professional work and that the very least you can do is to do so now, in addition to apologizing (note how Miss Manners snuck in that second apology).

DEAR MISS MANNERS: My niece was recently married for the second time, and as she had a formal wedding the first time, she chose to have a small, intimate ceremony in her garden this time. She invited her parents and her brother, but no other family members.

This seems reasonable for a second marriage. However, I found out about her wedding through a neighbor, who saw it online. I called her to congratulate her, and she said that she hoped to have a reception sometime in the future, to which extended family would be invited.

I don't know what to expect. Should I sign up for the social media platform on which my neighbor saw the news, just in case she announces the reception in the same way she announced the wedding? Is there a kinder way to announce a wedding to which very few were invited, and to extend an invitation to a future reception?

GENTLE READER: The problem with your niece's modest (and, as both you and Miss Manners agree, praiseworthy) approach to sharing her good news is that it is inconsistent with shouting it from the rooftop. Trust that if, and when, she does throw a reception, she knows where you live.

DEAR MISS MANNERS: My husband and I had houseguests wall-to-wall last summer -- some departing and arriving within hours of each other. We were amazed that people who stayed for several days did not offer to take us out to a meal during their visit.

We were constantly hustling chow, taking them to see the sites and providing entertainment. From them -- nada.

Is thanking your hosts with a meal an old-fashioned idea?

GENTLE READER: Apparently, from what Miss Manners hears. But it is still on the books, regardless of the numbers of scofflaws.

(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: Living in a city that generates massive quantities of plastic waste on a daily basis, I can't pass an overflowing garbage can or notice litter blowing down the street without thinking about where it will end up.

If I had my way, single-use plastic would be strictly limited to essential functions, such as in medical equipment or gloves to handle hazardous material. While plastic bag bans and paper straws are great steps forward, many businesses still seem to use way more plastic than is necessary.

I wish more businesses encouraged their staff to ask customers before adding, say, plastic utensils to a food order or a plastic sleeve over dry-cleaned items. While I would like to feel more comfortable asking business owners to consider making these changes, I'm not sure how to do it in a way that is polite and kind. I don't mean to cause offense, and the last thing I would want to do is annoy staff who are just doing as they're instructed.

When I have made requests to people in my own life to be mindful of their plastic consumption, they have responded defensively, leaving me feeling even more cautious about approaching strangers. As the ocean fills rapidly with our plastic waste, do you have any suggestions for ways to handle these conversations respectfully?

GENTLE READER: We live in a very imperfect world. Fortunately, many people feel compelled to right wrongs -- just not always the same ones.

But we can all agree that our cause is too important to give way to others' -- or to normal rules of decorum, like not haranguing strangers in the street. Miss Manners would have thought it was self-evident that doing so is counterproductive.

Make your case to people who are able to effect change -- at times when they are listening, and using language that will convince, not alienate, them. Such an approach will not improve things as quickly as you want, but it will do so more quickly than arguing over whose injustice is the worst.

DEAR MISS MANNERS: I found out through social media that my ex-father-in-law passed. My ex-mother-in-law posted a photo from a celebration of life that had been held for him.

My ex-husband's new wife forbade him from having any contact with me, but I am still friends with his mother online (although I am careful not to like or comment on her posts).

Would it be all right if I were to send her a condolence card, or should I just ignore it? There was no post made when he passed, just the one mentioning the celebration of life. Is it too late?

GENTLE READER: The opinions of current spouses regarding with whom you should, or should not, associate should be heard, if not necessarily always followed. Those of former spouses have no such standing.

Miss Manners does not mean to encourage you to do something merely to annoy. But sending a condolence note is a kindness to your former mother-in-law, not an intentional affront to your ex-spouse or his new wife. Explaining any passage of time is as easy as noting that you only recently became aware of her loss.

(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: When did "RSVP" cease to mean "Please respond, yes or no" and come to mean "Respond only if your answer is yes"? I receive a lot of e-vites and such, and they all seem to imply this new interpretation of the old phrase.

It feels a little rude not to be offered a gracious way to opt out that doesn't involve not responding at all.

GENTLE READER: Can we please do away with that form? Apparently nobody understands it -- did everyone fail high school French? -- and it is now annoyingly used as a noun.

It means "please respond."

Yes, as those of you who did ace high school French will point out, the phrase is actually "if you please," but the "if" is not supposed to be taken literally. It is safe to presume that few people, even those who give large parties, can prepare adequately when they do not know how many guests they will have.

Miss Manners would think it obvious that it is rude to ignore an invitation. But most people only seem to find that out when they are the hosts.

So let's put it in plain English: "Please respond." The more formal version is "The favor of a reply is requested." Notice that Miss Manners does not use the British spelling, "favour" -- why all the foreign phrases? -- nor does she condone "Regrets only." It is not for the host to presume that a prospective guest would regret skipping the party.

DEAR MISS MANNERS: I had a "friend"/co-worker stab me in the back and betray my trust. She has no clue that I know, and she keeps asking/pushing me to go to lunch with her.

How do I politely decline so as not to cause friction? I don't trust her and prefer not to associate with her, but unfortunately I see her regularly.

GENTLE READER: Probably any other adviser would tell you to have it out with this person, explaining that you were hurt by her betrayal.

Not Miss Manners.

At best you would get an apology, which would not necessarily ensure its not happening again. But you might instead get a denial, a justification or a counter-accusation. If she really regretted what she did, she would have found a way to make that clear.

You have to work with this person. You have discovered that she is not a friend. So treat her only as a co-worker. That means that politeness is required, but not warmth -- nor lunch, nor other opportunities to talk it out. "Sorry, I'm busy" is all that is needed.

DEAR MISS MANNERS: I want to thank the U.S. Postal Service for delivering a card addressed to me by my mother, who was severely visually impaired. Her handwriting was terrible and this letter was handled with TLC to get it to me!

This was the last piece of mail I received from Mother before she died, and I am very grateful to those who recognized the love and effort that she put into sending it.

GENTLE READER: So do it -- thank your local post office, and perhaps write a letter to the Postmaster General. Miss Manners suspects that they do not get a lot of gratitude from the public.

(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.)