If you write a tweet which starts with @, it won’t be seen by many people.

For instance, if your tweet starts with @carolinefiennes, it will only be seen by people who follow both me and you. That may not be many people. If you want people to know that “@carolinefiennes has written a marvellous article”, you would do better to write a tweet which doesn’t start with @. For example “.@carolinefiennes has written a marvellous article” or, better, “Read this marvellous article by @carolinefiennes”

Tweets which start with @ are public – they can be seen on your ‘tweets and replies’ page – but don’t get seen by many people who don’t go looking for them.