Dec. 14 (Bloomberg) -- Unless you follow the ins and outs of politics along the Bayou, you probably missed this week’s resignation of Jim Letten, the longest-serving U.S. attorney in the country.

Why did he resign? “Beginning last spring,” the New York Times informs us, “a series of legal motions had revealed that Mr. Letten’s senior prosecutors had been making provocative, even pugnacious comments about active criminal matters and other subjects under aliases at nola.com, the Web site of The Times-Picayune newspaper.”

Letten, the U.S. attorney for the Eastern District of Louisiana, was widely respected for his vigilance in rooting out public corruption. That he was brought down by his staff’s inability to resist joining Internet comment threads would hardly have surprised the journalists of a century ago, who fought for the right to sign their articles precisely to preserve the integrity of their words. They understood the dangers of anonymity. We have forgotten.

Complaints about rudeness in the online world are hardly new, of course. But we are way past incivility now. Even making allowances for the inevitable trolls, comment threads have grown increasingly wild -- so wild that legal consequences have begun to ensue.

No Name

Consider the contretemps that erupted this past summer, when a newspaper in Spokane, Washington, resisted demands that it identify the anonymous commentator who posted this unflattering reference to a Republican Party official in neighboring Idaho: “Is that the missing $10,000 from Kootenai County Central Committee funds stuffed inside Tina’s blouse?”

The newspaper was threatened with litigation. Its own staff was divided over whether protecting the identity (in practical terms, the IP address) of a commenter rose to the same ethical level as protecting the identity of the anonymous source for a story. A confrontation was avoided when the person who posted the comment outed herself. But it’s fair to ask whether she would have posted the insinuation had she known that her name would later be attached to it.

There is something charmingly attractive about keeping one’s identity secret while telling one’s story to the world. The Supreme Court has rightly held that anonymous commentary is protected by the First Amendment. Whistle-blowers need protection against retaliation, as do those pushing unpopular political positions. During the heyday of the civil-rights movement, the ability to keep from public view the identity of members was considered a hallmark of the freedom of association.

Alas, anonymity is not always pressed into the service of such noble ends. On the contrary: More and more, the online-comment thread seems diabolical -- in the medieval sense of the word, as the devil’s invention to bring out the worst in us.

In April, a Texas couple won a $13 million defamation judgment against individuals who had posted anonymous accusations that they were sexual deviants and drug dealers. Topix.com, which hosted the relevant message boards, was forced to turn over the writers’ IP addresses.

We should have seen all of this coming. The history of the movement against anonymous authorship is very much a story of trying to improve the quality of the published word.

Anne Ferry, in her classic article “Anonymity: The Literary History of a Word,” pointed out that terming a work “anonymous” gained popularity in the 16th century not as a way of hiding the writer’s identity, but as a means of identifying works -- poems especially -- whose authorship was unknown. Anonymity, in other words, was not a means of protection; its use, rather, conveyed information.

No Bylines

As newspapers and magazines rose to prominence in the 18th century, bylines as we know them today were largely avoided, creating the illusion that the publication spoke with a single voice. Still, the reader knew whose voice it was -- the publisher’s -- and thus understood whose views were being reflected, and who was responsible for them. As sociologist Michael Schudson points out in “Discovering the News: A Social History of American Newspapers,” even during the Civil War, when the public appetite for news was insatiable, people identified reportage by the paper in which it appeared; by and large, they neither knew nor cared who wrote what.

By the end of the 19th century, newspapers were being prodded to move from unsigned to signed news articles, partly because of a fear of corruption: Many unsigned articles, writes Schudson, were little more than news releases from the powerful. Reformers said unsigned articles were unethical.

In 1889, the novelist Tighe Hopkins weighed in on the side of disclosing the authors’ names, and his argument was typical: “It is, at all events, certain that anonymity opens the door to any facile hack,” he wrote in an essay in the New Review. “It is to the interest of the honest journalist that he should be known to the public.”

Journalists were not the only ones to confront the issue. A 1928 education textbook warned: “Students who hide behind anonymous replies to be smart and clever are more likely to take the task seriously if obliged to sign their names.”

This last passage nicely states the problem. Yes, anonymity can be handmaiden to courage and honesty. On the other hand, by lowering the cost of communication, anonymity can reduce the care that we put into our words. Most probably, the comments that led to Letten’s resignation were posted not as part of some carefully considered plan but rather on the spur of the moment -- impulsively, and thus thoughtlessly.

Many websites are moving away from anonymity, requiring those who wish to comment to sign on with Facebook, Google+, Twitter or some other account. (This is the case on Bloomberg’s website, where commenters can also register with Bloomberg.) Some popular blogs have ceased to permit comments at all.

Website operators are rediscovering the concern that motivated the move to newspaper bylines a century ago: Anonymity greatly heightens the risk of reckless and even harmful speech. The First Amendment protects thoughtless comments, but nobody is required to host them. Perhaps as Web discussions move in a less anonymous direction, the quality of conversation will improve.

I am saddened by the decline of the anonymous comment, for reasons I have already mentioned. And it is true that there is silliness aplenty on Facebook and Twitter, too. Still, it is my hope that we will discover, as newspapers did long ago, that few things are as conducive to thinking carefully about what to say as being required to sign your name.

(Stephen L. Carter is a Bloomberg View columnist and a professor of law at Yale University. He is the author of “The Violence of Peace: America’s Wars in the Age of Obama,” and the novel “The Impeachment of Abraham Lincoln.” The opinions expressed are his own.)

To contact the writer of this article: Stephen L. Carter at stephen.carter@yale.edu or @StepCarter on Twitter.

To contact the editor responsible for this article: Michael Newman at mnewman43@bloomberg.net.