DEAR MISS MANNERS: My girlfriend is somebody I’ve known for quite a long time -- the past five years, to be exact, though we only just started dating three months ago. I think it’s worth mentioning that I’m 17.

Since our introduction, we became extremely close, closer than any of our other friends, and have made a stack of memories. We’ve also had plenty of disagreements and many arguments, and we almost stopped talking altogether, other than an occasional text message here and there, for several months. But we started talking again, and then she persistently pursued me for a year before I finally asked her on a date.

My point is that we have a past. I love her to death. In fact, I’m considering the idea of marriage, which is a topic I’ve always been against. I try to show her my feelings all of the time, too, and she claims to really appreciate it.

This isn’t to confess my love, but rather it’s because I’m worried she’ll get sick of my love eventually. For a while she said that I’m a “mystery” to her. But as I open up to her and become more vulnerable, will she become bored of me, with the loss of vagueness? Am I just overthinking this, or if I’m not, how should I go about avoiding that?

GENTLE READER: Welcome to the human condition.

Of course you are overthinking this; people do when they are in love. But Miss Manners promises you that by the time you are old enough to be married, you will have the answers to your questions -- at least in this particular case.

DEAR MISS MANNERS: I am a 20-something male in a one-bedroom downtown apartment, and I have inherited a large collection of family heirlooms. My grandmother was a prolific home seamstress who took pride in her work. She tagged and saved a number of really beautiful textile samples that were made with great care during her generation and that of her parents.

While I treasure old things, these fragile, unstylish, century-old, hand-woven, hand-sewn heirlooms should have passed, mother to daughter, to somebody else. But there is nobody else, and I find the odds quite slim I’ll meet someone who will actually care about them in my generation.

How can I show respect to these heirlooms and their curators, for which I have neither space nor lifestyle to truly care for?

GENTLE READER: The plain rule is that once something has been given to you, you may dispose of it as you will. But Miss Manners is pleased that you have a sense of piety for your grandmother’s treasures. You -- and she -- will feel better if you offer them to a textile museum or local sewing or quilting club.

DEAR MISS MANNERS: If I am not mistaken, controversial subjects like religion and politics are things that should be avoided at social functions, or almost anywhere else, for that matter. What is your advice when it comes to conversations about politics??

GENTLE READER: Duck.

(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.)

GENTLE READERS: As Miss Manners recalls, there were two purposes to the 19th-century Grand Tour. Privileged youths were sent abroad by their indulgent parents to acquire culture and to enjoy what was not yet called a “gap year” before settling down to serious business and family-sanctioned marriage.

Hence the bad reputation of tourists for grabbing cultural artifacts and indulging in nonsanctioned encounters. But the idea was that no one they cared about would know, as all that happened in the faraway places where they had misbehaved. The disgust of foreigners was not thought to affect the reputations of those who would not have gotten away with these antics at home.

We know from the internet how empowered people feel to be obnoxious when they think they are anonymous. But for tourists, those etiquette-free times abroad are becoming risky. Destination countries are fighting back with laws, and their citizens are fighting back with video cameras. If you are arrested and fined a good chunk of your travel budget, or your boorish behavior is posted online, it is not safe to assume that no one back home will know.

Truthfully, Miss Manners hates tourist-bashing. (Full disclosure: She travels; therefore she is a tourist.) And she deplores the silly snobbery by which some tourists carry on about how they hate tourists, and only go to places “where none of the tourists go.” Never mind that this would no longer be true once they set foot there.

Over the years, she has defended tourists from petty insults. So what if they used to wear drip-dry clothing? They had no access to irons. Anyway, the locals are now wearing the same current American look of jeans and sweatshirts.

Good for the tourists who try out the languages they studied in high school, and if their accents aren’t exact, well, neither are those of the foreigners who scornfully answer them in English.

Yes, tourists often travel in groups, but that is a way of dealing with logistics that may be difficult for novices or others. And if they go to many places for quick visits, perhaps they are sampling in order to find a place they will later explore more deeply.

But Miss Manners condemns outright rudeness wherever it occurs, and there are striking examples of it among the 21st-century Grand Tourists:

Wearing beachwear in cities. Attempting daredevil stunts in historic sites. Making excessive noise. Blocking people and otherwise making nuisances of themselves to take selfies. Littering. Urinating in public. Copulating in public.

Stop it -- if not because all this is despicable, at least do so to protect yourselves from local reprisals. And also because Miss Manners knows that people who believe that it is all right to behave badly anywhere will soon come to believe that it is all right to behave badly everywhere.

So when foreigners ask, “Why can’t they act the way they would behave in their own hometowns?,” she worries.

DEAR MISS MANNERS: Can I give my grandson’s girlfriend something for her hope chest?

GENTLE READER: Not unless you know for certain what your grandson’s hopes 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: Somewhere in the midst of my extended education, I have significant knowledge gaps -- gaps that no one else seems to have.

I am American and live here now, but grew up and was educated abroad. I also have an ardent love of history and all things of the past, which is the focus of much of my time and energy. These two factors leave me susceptible to not understanding what people are talking about in common conversation.

This happens often. Sometimes I admit to not knowing what or who is being discussed, and am half-jokingly dismissed/excused: “Oh, she’s just from XYZ.” Other times I keep silent.

Is there a way to ask someone to clarify or add context that will allow me to know who or what is being discussed while saving face? Would I be rude for asking and interrupting the flow of conversation, or is the speaker rude for assuming knowledge on the part of listeners?

GENTLE READER: In this era of 24-hour entertainment, it seems highly unlikely to Miss Manners that any one person could possibly recognize every reference made in casual conversation.

If you find yourself lost, you may interject for clarification without shame -- and even make your own references as counterpoints. That is how conversation works. And while comparing the latest viral video to the imagery of Baudelaire will probably not make you friends, it will certainly make your point.

DEAR MISS MANNERS: Two years ago, a high school classmate who had done extremely well in the business world invited me to her 65th birthday celebration, held at her farm. Because I live many states away, she invited me, as well as one of my other classmates who was coming in from out-of-state, to stay with her.

This birthday was a big bash: catered, with well over a hundred friends and business associates attending, most of them staying in nearby hotels.

I spent a considerable amount of money on airfare, car rental and an expensive birthday gift to attend this event. I sent the gift ahead of my travels via express mail. I did get a text from the birthday person, thanking me and saying she loved the gift.

Should I have sent her a written thank-you for staying with her, even though it was her birthday party? And should I have expected a written thank-you from her, even though I did get one via text message? What is proper in this day and age?

GENTLE READER: Thank-you letters are never remiss. An even exchange may seem redundant, but Miss Manners assures you that the reasons for sending them in this case are entirely different, even if the overarching theme may be the same.

So yes, your friend should have sent you a proper letter to thank you for the present. And you should have sent one to thank her for inviting you to stay. That the occasion for both was to celebrate her is largely inconsequential.

(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.)