element-web/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_UserPill,
.mx_RoomPill,
.mx_GroupPill,
.mx_AtRoomPill {
    border-radius: 16px;
    display: inline-block;
    height: 20px;
    line-height: 20px;
    padding-left: 5px;
}

.mx_EventTile_body .mx_UserPill,
.mx_EventTile_body .mx_RoomPill,
.mx_EventTile_body .mx_GroupPill {
    cursor: pointer;
}

/* More specific to override `.markdown-body a` color */
.mx_EventTile_content .markdown-body a.mx_UserPill,
.mx_UserPill {
    color: $primary-fg-color;
    background-color: $other-user-pill-bg-color;
    padding-right: 5px;
}

.mx_UserPill_selected {
    background-color: $accent-color ! important;
}

.mx_EventTile_highlight .mx_EventTile_content .markdown-body a.mx_UserPill_me,
.mx_EventTile_content .mx_AtRoomPill,
.mx_MessageComposer_input .mx_AtRoomPill {
    color: $accent-fg-color;
    background-color: $mention-user-pill-bg-color;
    padding-right: 5px;
}

/* More specific to override `.markdown-body a` color */
.mx_EventTile_content .markdown-body a.mx_RoomPill,
.mx_EventTile_content .markdown-body a.mx_GroupPill,
.mx_RoomPill,
.mx_GroupPill {
    color: $accent-fg-color;
    background-color: $rte-room-pill-color;
    padding-right: 5px;
}

/* More specific to override `.markdown-body a` color */
.mx_EventTile_content .markdown-body a.mx_GroupPill,
.mx_GroupPill {
    color: $accent-fg-color;
    background-color: $rte-group-pill-color;
    padding-right: 5px;
}

.mx_UserPill .mx_BaseAvatar,
.mx_RoomPill .mx_BaseAvatar,
.mx_GroupPill .mx_BaseAvatar,
.mx_AtRoomPill .mx_BaseAvatar {
    position: relative;
    left: -3px;
    top: 2px;
}

.mx_Markdown_BOLD {
    font-weight: bold;
}

.mx_Markdown_ITALIC {
    font-style: italic;
}

.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;
}