nyastodon/app/javascript/styles/mastodon/rtl.scss

body.rtl {
  direction: rtl;

  .reactions-bar {
    direction: rtl;
  }

  .announcements__mastodon,
  .drawer__inner__mastodon > img {
    transform: scaleX(-1);
  }

  .compose-form .autosuggest-textarea__textarea {
    padding-right: 10px;
    padding-left: 10px + 22px;
  }

  .columns-area {
    direction: rtl;
  }

  .account__avatar-wrapper {
    float: right;
  }

  .column-header__setting-arrows {
    float: left;
  }

  .admin-wrapper {
    direction: rtl;
  }

  .react-swipeable-view-container > * {
    direction: rtl;
  }

  .simple_form .label_input__append {
    &::after {
      background-image: linear-gradient(
        to left,
        rgba(darken($ui-base-color, 10%), 0),
        darken($ui-base-color, 10%)
      );
    }
  }

  .simple_form select {
    background: darken($ui-base-color, 10%)
      url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 14.933 18.467' height='19.698' width='15.929'><path d='M3.467 14.967l-3.393-3.5H14.86l-3.392 3.5c-1.866 1.925-3.666 3.5-4 3.5-.335 0-2.135-1.575-4-3.5zm.266-11.234L7.467 0 11.2 3.733l3.733 3.734H0l3.733-3.734z' fill='#{hex-color(lighten($ui-base-color, 12%))}'/></svg>")
      no-repeat left 8px center / auto 16px;
  }

  .fa-chevron-left::before {
    content: '\F054';
  }

  .fa-chevron-right::before {
    content: '\F053';
  }
}