Damn, /nihongo/ threads like
(;;・m・) わたしわにほんごがわかりません。
save for me like
(;;�Em�E) �킽����ɂق񂲂��킩��܂���B

/nihongo/ board has Content-Type: text/html;charset=shift_jis , while almost every other board has it as text/html;charset=utf-8. And things break when I do AJAX like things from one board to another

xmlhttp.onreadystatechange = function() {

if (this.readyState == 4 && this.status == 200) {
  var page = document.createElement('div')
  page.innerHTML = xmlhttp.responseText.split(/<body[^>]*>((?:.|\n|\r)*)<\/body>/i)[1]
  //alert(page.innerHTML)
  page = document.evaluate('//*[@id="oldthreadlist"]', page, null, 9, null).singleNodeValue
  katalog_parse(board, page)
}

}