PEOPLE WHO boast that they "never apologize, never explain," or who claim that "love is never having to say your're sorry," ought to be ashamed of themselves and admit it and ask forgiveness.

Now that the duel is illegal, the apology is the only way left to settle many disputes without getting blood on the sofa. The duel got it on the grass, or on the Belgian sands, where it was biodegradable, or something. Anyway, it came out, which it doesn't on brocade.

A humble speech, a graceful letter, a box of flowers, a duplicate Etruscan vase to replace the one you merrily knocked over to dramatize a story -- what fault will these not erase?

Well, Miss Manners will tell you. One day a lady of our acquaintance asked what she should do after she and her husband failed to show up for a small, seated dinner party that a kind friend was giving in their honor. The engagement had simply slipped their minds, and the thought of these good people, standing about as the food congealed, waiting to do honor to cherished friends who never bothered to show up, was beginning to interfere with their sleep.

Miss Manners was quick to realize that there was only one thing this couple could do. That would be to change their names, move out of town, and take up a life of anonymous service to others. It is a course of action Miss Manners nearly followed herself, when a rare Trollape volume, lent to her by a kind stranger from a complete, matching and cherished set, disappeared from her desk. (The volume returned and confessed to having merely hidden to tease Miss Manners, a trick it had learned from observing her spectacles, and that is the only reason your Miss Manners is able to be with you today.)

So there are, indeed, unforgivable social sins for which there is no need to apologize because no apology would ever be adequate. (You will be glad to hear, however, that Miss Manners' spectacles apologized for having led astray the visiting volume, and the apology was accepted even though the promise of never doing it again was not believed. If a relationship is to continue, both sides have to be allowed to save face.)

Ordinary crimes of forgetfulness -- as the dinner engagement might have been if it had been a large party, or served from the buffet, and if the absent guests had not been guests of honor -- should be redeemed by an excess of thoughtfulness. One bombards the offended person with abject words, spoken and written, and with flowers until that person is exhausted enough to soften.

The only excuse, as in so many acts better left uncommitted, is temporary insanity. To say, "I was terribly busy," is another insult, meaning, "I had more important things to do than to take time or effort to think of you."

"That was such a dreadful, hectic time that I went out of my mind and neglected the very things that matter to me most" is more like it.

The best apology for material damage is material. But "Can I pay for it?" is no help, said, as it is, with the knowledge that it will bring a protest, however insincere. "Who does your reupholstering?" or, "What is your crystal pattern?" or, "Who is your antique dealer?" is infinitely more reassuring. In these cases, the bother, as well as the cost, should be assumed by the wrongdoer.

Exclamations of, "Oh, no, don't give it another thought" on the part of the offended hosts should be steadfastly ignored. After all, those are the same people who were just saying to you, "Oh, don't leave yet, it's early" -- just as if they meant it. MISS MANNERS RESPONDS

Q. Recently, my husband and I were invited to attend a business dinner party at a prominent area restaurant. Although I have severe hay fever, my husband insisted I accompany him. The dinner lasted several hours, during which time I had to blow my nose continually.

My question is this: Was it impolite for me to remain at the table, or should I have excused myself and gone to the ladies' room, although I would have had to do this dozens of times? I received several demeaning looks from the other guests, so I explained my hay fever was quite uncontrollable. I need an answer, because my husband's company has several of these functions throughout the year, many during the hay fever season.

A. Miss Manners will arouse herself from the state of silly amusement that came on when she printed guests delivering "demeaning looks" at a sneezer, and remember that nothing connected with human suffering is funny.

Your conduct should be regulated by the desire to create as little distraction as possible with your problem. A woman who gets up from the dinner table a dozen times during one meal would completely mesmerize the guests, leaving them with nothing on their minds but a maddening curiosity to know what was wrong with her. Similarly, a person who is constantly blowing her nose distracts the guests by making them wonder if they are going to catch what she has. Therefore, you were right to explain your illness.

What, then, brought on the demeaning looks? Possibly an unappetizing way of blowing your nose, which distracted the guests from the enjoyment of their dinners. Miss Manners advises you to carry large handkerchiefs (not tissues) and to learn to blow your nose without noise and without exhibiting any interest afterwards in the success of your temporary cure. This may not be clear, but Miss Manners does not know how to put it more plainly without doing distracting things to her own appetite.

Q. With the wedding a week and a half away and time running short for receipt of all the response cards for a catered, sit-down reception, I suppose I'm uptight.

Your advice will probably be late, but I'd just like to know how I was supposed to cope with responses that included uninvited guests. Children, in particular, were excluded from the invitation. Two guests asked the bride about bringing the child ("Never before excluded from the parents' coming and going"). Another couple's total included their child. Yet another guest (single guests were invited to bring a friend/companion) added two friends to the number of dinner guests to expect.

I'm probably allowing my mind to distort this cut of proportion -- but am I wrong to resent this behavior? What is the best, mannerly way to handle such situations?

A. If Miss Manners feels like weeping when she hears of how rudely people attempt to impose on those whose only crime is to invite them to a wedding -- and Miss Manners isn't even in the emotionally wracking throes of putting on a wedding -- how can she call your resentment wrong, or even out of proportion?

Do not listen to the pleas of parents claiming that umbilical cords have not yet been broken at any social event -- these are the very parents who will permit their children to whine aloud during the ceremony. Nor should you allow any guest to run his or her own party-within-the-party with a guest list not chosen by you. Even allowing single guests to bring their own friends is more than Miss Manners would do. A wedding is not a public entertainment.

The answer to how to deal with these outrageous requests is: firmly. "I am so sorry -- we are simply not having children," or "No, I'm afraid we're only asking our own dear friends to share this occasion with us." Do not allow these people to blackmail you by threatening their own refusals. The answer to that is, "Well, I'm so sorry you won't be able to come. It would have meant a great deal to all of us to have you there."

Q. Please be informed that I am a 71-year-old widow who prefers that all my mail be properly addressed: Mrs. John W. Johnson, my late husband's name and to whom I was legally married for a period of 41 years; not that of Mrs. Millie C. Johnson, as I am not a divorcee. Please, Miss Manners, for the information of my new daughter-in-law, and thousands of others as well, kindly and discreetly set them straight in print.

I find good in everybody and I love my dear, new daughter and certainly do not wish to hurt anyone, especially my beloved, late husband. I will appreciate your kind and prompt attention to my request as herein stipulated.

A. Miss Manners has been saying this for so long and so often that she cannot think how your daughter-in-law escaped hearing it. However, she will be glad to set it forth once again, for the benefit of good people who make mistakes and also -- Miss Manners harboring an occasional unworthy thought about human nature -- for the benefit of those who take satisfaction in annoying the bereaved with their questionably motivated misinformation.

A married woman's name does not change when her husband dies. Although there are many women now who never style themselves "Mrs. John" anything, those who do are correct in doing so during widowhood. Although using the title "Mrs." with a woman's first name is never correct, it is most often associated with divorce and is thus offensive to widows. (P.S. Miss Manners knows you mean well, too, but the correct traditional way to address a divorced woman is with her maiden surname and married surname directly after "Mrs."; and the new way is to use "Ms." with her given and surnames.)