I have never used Twitter or Facebook because I fear they would become a huge drain on my time. By contrast, Jalen Brown, a bright and gregarious 20-year-old undergraduate at Morehouse College in Atlanta, loves the give-and-take of those platforms. His contemporaries would think him odd if he didn’t.

Expressing himself on Twitter, however, got Brown suspended from Howard University in D.C. in 2019. He transferred to Morehouse but continued to apply for reinstatement at Howard, trying to show he had learned his lesson. He said he was devastated last summer when Howard informed him, without explanation, that he couldn’t return.

The calamitous effect of social media participation on Brown’s life is only a tiny part of the raging debate over the influence of chatter on major platforms. His case illustrates how confusing and sometimes traumatic are the largely unwritten school rules for online expression. How did a few words on Twitter get Brown in such trouble on one celebrated campus but not prevent his enrollment at another?

Brown was having what he thought was an interesting argument with a fellow Howard student when at 1:57 p.m. on July 19, 2019, he posted the tweet that got him thrown off campus. The other student had disagreed with Brown’s support of a campaign on behalf of students who had lost their scholarships because of bad grades.

Brown responded with this: “how do you publicly talk down to a group that’s doing their DAMN best to save the future of hundreds of students? harriet shot you n----s and we’ll do the same.” His reference was to the legendary abolitionist Harriet Tubman. He used a colloquial form of the n-word. Brown and the other student in the exchange are both Black.

As a longtime Tubman fan, the tweet upset me. The accusation, which Brown said he saw somewhere on Twitter, appears to be false. Catherine Clinton, a historian who wrote the wonderful 2004 biography “Harriet Tubman: The Road to Freedom,” told me there is evidence the anti-slavery warrior “threatened to shoot those members of her party who wanted to turn back during escapes.” But, Clinton said, “there is absolutely no mention or record of her actually shooting anyone.”

If the two students had been chatting in the Bethune Annex Café on campus, nothing may have come of their quarrel. Brown’s tweet, however, came to the attention of the authorities. He said he deleted it a day after posting because he thought he had gone too far. At his suspension hearing he begged for another chance, he said, but was told he had to go.

What should we do about outrageous threats and falsehoods? There have been a lot of them lately. I suspect this may be part of being an American. We are not known for restraint in how much we drink, how fast we drive or what we say and write.

Yet many of us rein ourselves in when we see we have gone too far. In an educational setting, I think, that admirable instinct is better encouraged by reasonable penalties than by suspending the offending student.

The Twitter and Facebook bans of President Trump might be a model. Universities could persuade the big platforms to penalize undergraduates who cross the line. Terrible tweets? No more Twitter for you this semester.

Brown told me he would have preferred that alternative. He said he doesn’t know why he was not readmitted, although his posts were still being tracked. He said one Howard official told him a tweet he posted last June 25 was “hostile.” Brown had tweeted that schools that reopened during the height of the pandemic “killed (yes, killed) their students for the sole sake of money.”

Howard public relations director Alonda Thomas said she could not comment on Brown’s case, other than to say university officials believed he had violated the student code of conduct. The code says “all students are guaranteed freedom of expression . . . provided that such activity is conducted in a reasonable manner, does not abridge the rights of others,” and is carried out in accordance with local or federal laws and university rules and regulations.

“Multiple times now,” Brown told me, “I’ve expressed now inappropriate and immature my tweet was. I have written multiple apology letters to multiple members of Howard’s administration.”

The student he was conversing with said in an open letter months later “I DIDN’T take it as a serious threat and almost forgot about it, until I received a call from a DCPD detective who mentioned it. The detective said that he had spoken to Jalen and didn’t consider the tweet a serious matter, either.”

Brown said Morehouse admitted him despite his trouble at Howard. “I showed them the tweet that led to my suspension,” he said. “I did not leave anything out.” A Morehouse spokesman had no comment.

Brown is a promising young man. He has received good grades and has written for student publications. He got into two of the best colleges in the country, as measured by the quality of their alumni. Vice President-elect Kamala D. Harris graduated from Howard. Nobel laureate Martin Luther King Jr., honored by a national holiday this month, graduated from Morehouse.

Brown said colleges like Howard might do better with some students on disciplinary committees. I think suspension and expulsion rulings may also suffer from too many lawyers. “The school doesn’t want to understand the mind-set of the student,” said Scott Limmer, a Mineola, N.Y., attorney who specializes in such cases. “They just want to punish so they can’t be called on the carpet if the student actually commits a violent offense at a later time.”

Colleges have many worries these days, but they also have much to teach their students. They can’t do that if they eject the young people who need those lessons the most.