I've had this problem for a while. No vertical line and no indentation (Five Template).
The following CSS insertion solved all the problems and allows for changing text colour and size as well. Obviously, colour, size and vertical line width can be changed to your preferences:
.
sqs-block-html blockquote, .sqs-block-markdown blockquote {
border-left: 5px solid #F0F19D;
padding-left: 20px;
color: #F0F19D;
font-size: 16px;
font-weight: normal;
}