pleroma-fe/instance/pleroma-mods/pleroma-mod-favicon/style.css

.instance-favicon {
  max-width: 18px;
  max-height: 18px;
  float: right;
  margin-right: -4px;
  margin-left: 4px;
}

.non-mention .instance-favicon, .status-preview-container .instance-favicon {
  display: none;
}