Crowdfunding website Kickstarter has surprised some of its users by replying to complaints they made seven years ago.

These included complaints about a book which some felt encouraged sexual harassment.

Users who received responses to long-expired projects from 2013 took to Twitter to congratulate the company on its response times.

Kickstarter replies to complaints from seven years ago https://t.co/VY8ZegRtxr

— BBC News Technology (@BBCTech) November 13, 2020

Kickstarter said the emails were "auto-generated in error".

But some of the complaints related to sensitive topics, annoying many who suddenly received a reminder.

The most prominent example cited online was about a book by a so-called "pick-up artist" that encouraged aggressive sexual behaviour.

The error dredged up an old argument over the book, which Kickstarter had refused to cancel on its platform, eventually publishing a blog post admitting a mistake on its part. But, by then, the creator had already received the money.

welp, someone at @kickstarter finally found the 'complaints' filing cabinet and opened it for the first time in seven years pic.twitter.com/TrflXgExXI

— dan hett (@danhett) November 12, 2020

The automatically-generated emails told people who had reported it to Kickstarter years ago, that the book did not violate its guidelines.

Other Twitter users posted examples of complaints that received a reply: one involved a robot that could supposedly control a cockroach, reported for animal cruelty; another was a copyright complaint about a card game using established characters.

Most, however, dealt with the controversial book.

Technology journalist Holly Brockwell was among those who received the email erroneously, telling her the project had not broken any guidelines.

"Seven years, and big tech hasn't improved its response to sexual assault and harassment at all," she tweeted.

"God knows why they're drawing attention to their total lack of sense seven years on."

After Kickstarter replied to her explaining the error, Ms Brockwell said that it was " Just.... a bit of a kick in the teeth of an email, you know?"

"Totally. We completely understand," Kickstarter replied.