DEAR MISS MANNERS: When issuing both formal invitations, such as to a wedding or dinner, as well as informal invitations, such as asking a friend to attend a movie together on the weekend, often a response is not received despite an RSVP date being clear. When I haven’t received a reply well past such a date, sometimes even sending a polite reminder, I assume it to be a no. However, I have had people ask me why I went ahead with the movie/dinner/other plans without them despite their lack of answer. I cannot figure out the proper response to this, other than, “You didn’t say yes by the date I …
