src/language-js/printer-estree.js/printIndentableBlockComment
function printIndentableBlockComment(comment) {
  const lines = comment.value.split("\n");

  return concat([
    "/*",
    join(
      hardline,
      lines.map((line, index) =>
        index === 0
          ? line.trimEnd()
          : " " + (index < lines.length - 1 ? line.trim() : line.trimStart())
      )
    ),
    "*/",
  ]);
}