Kindness online faces a genuine structural disadvantage: the physical and social cues that normally encourage considerate behaviour in person, eye contact, tone of voice, immediate visible reaction, are largely absent from a text-based exchange, which makes it considerably easier to say something in writing that would rarely be said face to face.
Deliberately compensating for this absence, reading a message twice before sending it, imagining the recipient as a specific real person rather than an anonymous account, tends to noticeably improve the tone of digital interaction, since much of online unkindness seems to stem from simply forgetting there is a person on the other end.
Communities that actively model and reward kindness online, rather than merely policing its absence after the fact, tend to see noticeably better behaviour overall, since tone in a digital space seems to be at least as contagious, in either direction, as it is in any face-to-face setting.