[JSWolf]

@hobnail, when you have classes together like in your CSS, Calibre will not remove any of the unused classes.

h1 {
  font-size: 1.44em;
  font-weight: bold;
  hyphens: none;
  margin-bottom: 0;
  margin-top: 1em;
  page-break-after: avoid;
  page-break-inside: avoid;
  text-align: center;
  text-indent: 0;
}
h2 {
  font-size: 1.3em;
  font-weight: bold;
  hyphens: none;
  margin-bottom: 0;
  margin-top: 1em;
  page-break-after: avoid;
  page-break-inside: avoid;
  text-align: center;
  text-indent: 0;
}
h3 {
  font-size: 1.12em;
  font-weight: bold;
  hyphens: none;
  margin-bottom: 0;
  margin-top: 1em;
  page-break-after: avoid;
  page-break-inside: avoid;
  text-align: center;
  text-indent: 0;
}
h4 {
  font-size: 1em;
  font-weight: bold;
  hyphens: none;
  margin-bottom: 0;
  margin-top: 1em;
  page-break-after: avoid;
  page-break-inside: avoid;
  text-align: center;
  text-indent: 0;
}

That is much nicer code.