DEAR MISS MANNERS: I was invited to a Halloween costume party, so I put together a costume and attended.

When I arrived at the hosts’ home, they were both dressed in costumes, and it was clear they had spent a lot of time and money decorating and providing quite a spread of music, food and cocktails for their guests.

It was a large group of about 60 guests, but I was very surprised to see that the majority of them, probably about 40, didn’t dress in costume at all. This seemed like a fun group of people, and not those whose finances would impede them from stopping at a Halloween shop for at least a simple mask, funny hat or the like.

I could tell the hosts appreciated my costuming effort, and I made no comments about the lack of participation from the other guests. At the end of the night, when I was saying my goodbyes, one of the hosts commented that she hoped to turn it into an annual event. She said that I would certainly be invited back, but “not everyone would be,” making me think she was also disappointed in her guests.

I suppose this doesn’t have to be about Halloween costumes, but following a dress code in general. If I invited a bunch of friends over to have a black-tie dinner party, and the majority accepted my invitation but then showed up in jeans and T-shirts, that would be rude, wouldn’t it?

GENTLE READER: Well, yes, although Miss Manners hopes you would interpret your dress code loosely enough to count a gentleman in a black suit or a lady in a nice afternoon dress as in compliance — just as you say that a mask or a hat would have been counted as meeting the costume requirement.

Dress codes are causing a lot of trouble these days. The ones you mention are clear and straightforward. Those who do not enjoy participating in costume parties or formal dinners should simply decline those invitations.

But there are hosts who issue unreasonable and even incomprehensible instructions. Declaring a color scheme, for example. Or coming up with an oxymoron, such as “Festive-Casual” or “Fashionably Laid-Back.”

Such things only annoy the guests. Hosts should state only the level of formality and trust their guests to dress themselves accordingly, however risky that may be. They should not attempt to costume them — unless they are actually giving a costume party.

Please send your questions to Miss Manners at her website, www.missmanners.com; to her email, [email protected]; or through postal mail to Miss Manners, Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106.