The creator of a data-driven fact-checking tool for the French presidential election says data journalists should welcome having their own work fact-checked by readers – and says “trolls” who question your methodology can become an asset.

Sylvain Lapoix, a senior journalist at online news site OWNI, has just finished working on Véritomètre – a fact-checking tool analysing the statistical claims made by the presidential election candidates during the campaign – and which took a year to build.

He said the project was inspired by US political journalism and had not been done properly in France before.

In France, there is a tradition in political journalism which is mainly a Voltaire way of doing things – a very literary way. Politics is about speech, attitude, how you behave. Getting numbers and all the facts back into the subject was a (challenge) we had to go through.

Speaking at the News World Summit in Paris today, Lapoix said:

One thing we learnt is that when you’re a data journalist or a web journalist, you should never ever ever – I insist – ever assume that your readers won’t look that close into your own (work) because eventually they always do.

A guy actually did all the maths from the quotes we fact-checked. At some point we considered him a troll – but he was taking it very seriously so we decided to answer to him.

Lapoix said he eventually “became an asset” to them. He added:

Your readers are your biggest database of experts you could ever have. They realise they matter to journalists. At some times the readers were defending us against other readers who were doubting us.