Okay, now I'm confused. What's the point of a limit if it doesn't make the card decline a transaction at the register?
It's like being 15 minutes late to work. One time and you probably won't be fired, but that doesn't mean there's no "point" of a start time. It just means that if you are an otherwise good employee, you'll likely be given some grace.
The article lists possible things that happen--varies by card--if you go over the limit. Some do decline the charge, but they might also increase interest, lower your limit after that charge, make you pay immediately instead of your due date, or other things. The 'point' of the limit still stands. The bank doesn't want to lend you more than that and won't longer term, but they may forgive the occasional mistake, especially if you have a strong history of paying on time and the overage is a rare exception.