If you can’t say something nice, don’t say anything at all. It’s a simple enough rule that most of us learned as young children. So why is it that some readers seem incapable of holding back from telling an author that they didn’t like their book?

It is a lesson one reader might have heeded before addressing the writer Nina Stibbe with some feedback on her 2013 novel Love, Nina: “My #bookgroup really not loving #lovenina. Voted it 1.3 (out of 10). Our lowest EVER score in 5 years and 60 books. Sorry @ninastibbe.”

Aside from the score – how on earth did they reach that .3? – the “sorry” makes it sound like Stibbe was on tenterhooks for her feedback. She wasn’t. But she did retweet the comment, much to the amusement of fellow writers who then shared their experiences of similar reader over-shares. The Latte Years author Philippa Moore’s experience was typical. “I was tagged in an ‘I won this book, didn’t like it, gave it to my mum’ Instagram post once,” she said. “I was like WHY DO I NEED TO KNOW THAT?”

A while ago, I posted a tweet congratulating JoJo Moyes on the success of the film adaptation of Me Before You. Within minutes I was in middle of a heated attack on Moyes by campaigners angry at Hollywood’s treatment of disability. Each angry tweet tagged Moyes, even though she was the writer not the producer. Like being raged at by a belligerent drunk at a wedding, it was neither the time nor the place.

Every author I know has been tagged by readers like this. Usually the reader announces they have reviewed the author’s latest novel. Only it’s a vicious review, awarding two stars (one for arriving on time). Why would they announce that to the author?

Crime writer Alex Marwood says snippy comments directed at her come through her Facebook page, which is meant to be for fans. One reader kindly told her she was “a craptastic author”. Another delighted in telling her about a scathing Amazon review (since removed), which Marwood later printed off and framed.

What is telling is that in almost every case – including that of Stibbe – the reader removes their original comment soon after it has reached its target. Could sudden self-awareness be at work? It is as hard to fathom as it is to know why they tagged the author in the first place.

Alex Marwood’s treasured Amazon review

Of course, social media have provided direct access for the kind of green-ink comments that used to be posted to publishers, such as the reader who was so incensed by Alex Brown’s use of the word “trellis” that she wrote to Brown’s MD at HarperCollins complaining: “It ruined the book for me.” These days she could have saved the price of a stamp and tweeted Brown.

But why bother? Like trolls, many of these tags are triggered by a single issue – top of the list is feminism (they hate it), closely followed by God (they love him) and politics (don’t go there). Some hint at being frustrated writers, who want to put smart-Alec authors in their place. “I prefer proper books, properly written. No offence,” snarked one reader to novelist and playwright Jonathan Harvey.

Others seem genuinely to think they are helping the writer by telling them they hated their latest work. All seem blissfully unaware that as a far as the author is concerned, their feedback is unwanted. Their tweet or post is on a level with a stranger shouting abuse in the street.

This cognitive dissonance is rooted in the collaborative effort that animates all prose fiction. No other art form is so intimate. Authors’ words inhabit the imagination of the reader and in one sense the act of reading completes a novel, as the reader reimagines the world created by the author.

But disaffected readers should remember who they are dealing with when they tag authors like this, because writers have a habit of taking revenge in print. When Tony Harrison wrote his poem Bringing Up, he used it to kick back at his father, who had been a harsh critic of his first collection, The Loiners. Had it not been a library book, Harrison senior declared, he would have thrown it in the fire. But his son struck back at the old man, lampooning him with his own words in the final line of the poem: “You weren’t brought up to write such mucky books!”