message: Do not remove diff signs from DOM unless GitHub feature is not supported
diff: @@ -3,6 +3,14 @@ import select from 'select-dom';
  import observeEl from '../libs/simplified-element-observer';
  function removeDiffSigns() {
  + // Return early for GitHub DOMs that exclude + and - when copying from diffs.
  + // Continue to support older GitHub versions such as users running GitHub Enterprise.
  + if (['deletion', 'context', 'addition'].some(name =>
  + select.exists(`.blob-code-marker-${name}`)
  + )) {
  + return;
  + }
  +
  for (const line of select.all('.diff-table > tbody > tr:not(.refined-github-diff-signs)')) {
  line.classList.add('refined-github-diff-signs');
  for (const code of select.all('.blob-code-inner', line)) {
  