pleroma/app/styles/components/display-name.scss

.display-name {
  display: block;
  max-width: 100%;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  position: relative;

  bdi {
    min-width: 0;
  }
}

.display-name__account {
  font-size: 14px;
}