.AuthorshipMarkers {
  float: left;
  width: 1cm;
  height: calc(100% - 5em);
  overflow-y: hidden;
}

.AuthorshipMarkers__Section {
  height: 100%;
  width: 4px;
  float: right;
  position: relative;
}

.AuthorshipMarkers__Marker {
  position: absolute;
  right: 0;
  border-left: transparent 2px solid;
}

.Presence__User {
  position: relative;
  border-left: 4px solid transparent;
}
.Presence__User input[type=color] {
  width:1cm;
  position:absolute;
  right: 0;
  top: .05cm;
}

.AuthorshipMarkers {
  float: left;
  width: 1cm;
  height: calc(100% - 5em);
  overflow-y: hidden;
  padding-right: 2px;
}

.AuthorshipMarkers__Section {
  height: 100%;
  width: 4px;
  float: right;
  position: relative;
}

.AuthorshipMarkers__Marker {
  position: absolute;
  right: 0;
  border-left: transparent 2px solid;
}

.Presence__User {
  position: relative;
  border-left: 4px solid transparent;
}
.Presence__User input[type=color] {
  width:1cm;
  position:absolute;
  right: 0;
  top: .05cm;
}

Add a padding to make room for chrome's contenteditable border
Styling: Add a padding to make room for chrome's contenteditable border
