THE MORAL indignation with which children assert their rights to privacy from their parents is awesome. Fortunately, they are rarely troubled at that time with memories of how grateful they once were to have these same invaders seek into the state of their diapers.

Parents do remember, however, and it sometimes hampers them in Miss Manners the granting of increasing rights. Miss Manners is a great believer in privacy within the family--for everyone--but she recognizes that diplomatic genius is sometimes required to deal with conflicting and confusing claims. She has therefore decided to undertake the job.

First, there must be the recognition that everyone old enough to have a secret is entitled to have some place to keep it. There is such a thing as an innocent secret. Those who believe that only the guilty have anything to hide from their relatives deserve to go through life without ever receiving birthday surprises.

Miss Manners finds the whole matter of searching for contraband quite distasteful, and forbids it among adults, who simply have to collect their evidence against one another without violating the law of privacy that applies to desks, files, drawers locked and unlocked, purses and wallets.

The conflict arises in regard to children only when it touches on possible crucial matters of health. The Diplomatic Pouch Rule (We're not allowed to search your pouch, and if we don't find drugs we're in deep trouble--but if we do, too bad) as applied to children must at least be decently disguised: "I was only cleaning your room, trying to get into all the corners, and you can imagine my shock when . . ."

And even then, one can only produce incriminating objects. A diary is an extension of the writer's mind, as letters are of the sender's; Miss Manners admits of no circumstances under which these may be read by others. But for small children only, one may read the envelopes for purposes of remarks such as "I see you got what looks like a birthday invitation. Don't forget to answer it right away, and let me know when you need to get a present."

Telephone calls are also scrutiny-free. It is legitimate to say "Tell whoever it is to call back after dinner," or "You'll have to wind up because I need the phone now," but not "What did Sean want?" or "Who was that you were giggling with?"

Then there is the trickier matter of privacy on the outside concerning what family members legitimately observed at home. Children are more likely to understand that, as their temptation is as great to regale their friends with funny stories about mommy and daddy as ever the parents' is to speak of them.

A fair deal would be something like this:

"I will check with you on what cute stories I tell about your little mishaps and sayings, and throw out the ones that most offend you, provided that you clear things with me before reporting them in Show and Tell or to my friends' children."

Evidence of bad behavior is always a family secret, which even the victims of it are enjoined from reporting for the amusement or sympathy of their friends. Extreme emotions, including falling in love and weeping fits, are the property of the person to whom they happen, not news to be disseminated without permission. Questions from outsiders about what other family members think of them should not be answered. Facts pertaining to money, people's whereabouts and such may be labeled secret by family agreement.

Miss Manners does not believe the clever child will have trouble negotiating such privacy. He need only report what he has learned from the examples given by his friends in health and hygiene class. MISS MANNERS RESPONDS

Q. What should I say when acquaintances and associates make snide remarks about my always wearing hats outdoors during the day? My friends don't make such comments, of course, as they understand.

For more than five years, I have had skin cancers, off and on. They are removed by surgery by a dermatologist who specializes in this ailment. On one occasion, I had to have radium treatments for a cancer that surgery couldn't remove, even with three tries.

My doctor insists that ultraviolet rays even come through the clouds on gray days, and that I wear hats with brims or carry an umbrella or parasol, which are cumbersome. As a result, I spend more time trying to find attractive hats than looking for suits and dresses. I remove the hats indoors, and then, of course, my hair is mussed and has to be combed.

What can I say to the people who tease me unkindly? I just smile at those who simply look amused.

A. Alas, what can anybody say, in a world where a lady is presumed to need a medical excuse to wear a hat? Indeed, where, by your account, even that is not sufficient?

Miss Manners thought that everyone knew that a lady always wears a hat when she leaves her house, and may keep it on, if she wishes, in offices and other people's houses. A sensible lady will use an umbrella or parasol as well outdoors, but unfortunately, Miss Manners is the only such sensible lady left.

However, it has always been proper for others to make teasing remarks about ladies' hats, and provided they are good-natured, you should just give that same smile. Those who tease unkindly may be told, "Oh, I had so hoped you would like it." That should arouse medium shame; if you want high shame, you may give your medical excuse.

Miss Manners must warn you, however, that people who deserve the high shame treatment never understand that they have received it.

Q. I am a male graduate student at a midwestern university, who is unfortunately not in possession of an automobile (I am sure that Miss Manners is aware that in the American heartland, lacking an automobile is considered equivalent to lacking other physical attributes integral to the masculine gender), and I would like to invite a lady to accompany me to dinner and the theater.

I walk everywhere, but I assume it would be the height of rudeness to ask someone wearing high heels and hose to walk 1 1/2 miles on a wintry evening. As a taxi is out of the question (if I tell Miss Manners that my subject of study is opera, she will understand that dinner out by itself means that I forgo dinner, in or out, for the next few days), is there a graceful, and, more important, correct way that I can suggest that the lady--whom I know to have an auto--drive us both?

A. The correct way is to say to the lady, after issuing your invitation, "We have to allow some time to go by public transportation (bus, subway or whatever your city offers), unless, of course, you would care to drive."

Miss Manners sees nothing whatever wrong with this. She does see something seriously wrong with ladies who confuse mechanical appliances with the essential characteristics of a gentleman, and would sternly warn any gentleman, with or without an automobile, against involving himself with such a lady.

Q. I am hurt, and wonder if I have a right to be.

I have a friend who is also a confidant, and whom I have known 20-plus years. Several times during the last two or three years, things I have told her confidentially have leaked through her husband--either back to my husband or to other friends. Recently, when I finally confronted her about the most recent issue, she admitted that her husband had, indeed, said "something," but that it was so "unlike" him.

I told her that I couldn't trust her husband, and she acted insulted and offended.

I realize that if I tell her things, she will most likely tell her husband. I also appreciate the fact that that is what most wives do. Therefore, I am left with the distinct impression that I should no longer confide in her, but she has made me feel that she is not the one who has misbehaved and therefore she still deserves my trust.

Was I wrong to confront her? Would any sane person continue to share secrets under the circumstances? I really feel bereft, because she was my only confidant.

A. Yes, you were wrong, and no, no sane person would continue to make confidences to an open-ended couple.

As you rightly recognize, a secret told to half a married couple is a secret told to all of it. You cannot reasonably expect your friend not to pass on your secret to her confidant--you told it to yours, didn't you? And it was your secret.

That, however, was your mistake, and Miss Manners advises you not to make it again. But a mistake of judgment is nothing compared to the etiquette mistake of informing a lady, truthfully or not, that her husband is a blabbermouth.

Feeling incorrect? Address your etiquette questions (in black or blue-black ink on white writing paper) to Miss Manners, in care of this newspaper.

Copyright (c) 1983, United Feature Syndicate Inc.