IN the beginning, the technology gods created the Internet and saw that it was good. Here, at last, was a public sphere with unlimited potential for reasoned debate and the thoughtful exchange of ideas, an enlightening conversational bridge across the many geographic, social, cultural, ideological and economic boundaries that ordinarily separate us in life, a way to pay bills without a stamp.

Then someone invented “reader comments” and paradise was lost.

The Web, it should be said, is still a marvelous place for public debate. But when it comes to reading and understanding news stories online — like this one, for example — the medium can have a surprisingly potent effect on the message. Comments from some readers, our research shows, can significantly distort what other readers think was reported in the first place.

But here, it’s not the content of the comments that matters. It’s the tone.

In a study published online last month in The Journal of Computer-Mediated Communication, we and three colleagues report on an experiment designed to measure what one might call “the nasty effect.”

We asked 1,183 participants to carefully read a news post on a fictitious blog, explaining the potential risks and benefits of a new technology product called nanosilver. These infinitesimal silver particles, tinier than 100-billionths of a meter in any dimension, have several potential benefits (like antibacterial properties) and risks (like water contamination), the online article reported.