A simple & non-obtrusive (I hope!) RTL stylesheet for Trello with Vazir font.

trello.css

pre {
    direction: ltr;
}

body, button, html, input, select, textarea {
    font-family: "Helvetica Neue", Vazir, Arial, Helvetica, sans;
}

.comment-container {
    line-height: 1.5em;
}

.markeddown ul>li {
    margin: 8px 20px 8px 0;
}

.checklist-items-list {
    direction: rtl;
}

.checklist-item-checkbox {
    left: initial;
    right: 5px;
}

.checklist-item {
    padding-left: 0px;
    padding-right: 26px;
}