element-web-Github/res/css/views/elements/_RichText.scss

// XXX: bleurgh, what is this? These classes totally break the component
// naming scheme; it's completely unclear where or how they're being used
// --Matthew

.mx_Markdown_BOLD {
    font-weight: bold;
}

.mx_Markdown_ITALIC {
    font-style: italic;
    /*
    // interestingly, *not* using the explicit italic font
    // variant seems yield better results.

    // compensate for Nunito italics being terrible
    // https://github.com/google/fonts/issues/1726
    transform: skewX(-14deg);
    display: inline-block;
    */
}

.mx_Markdown_CODE {
    padding: .2em 0;
    margin: 0;
    font-size: 85%;
    background-color: $rte-code-bg-color;
    border-radius: 3px;
}

.mx_Markdown_HR {
    display: block;
    background: $rte-bg-color;
}

.mx_Markdown_STRIKETHROUGH {
    text-decoration: line-through;
}