What is the pipe-like (or border-left) character in front of PDF excerpts?

I see it on what I think is the default CSS and with the CSS below, but the pipe character (or border -left) is still there. Any suggestions? Thanks!

/pdf highlight/
.rem-reference–pdf-highlight {

border-color: transparent;
border-bottom: solid slateblue;
border-width: 1px;
color: slateblue;
border-radius: 0px;
text-decoration-color: slateblue;

.rem-reference–pdf-highlight::before {
content: "{ “;
color: #ccc;
.rem-reference–pdf-highlight::after {
content: " }”;
color: #ccc;

Ah, thanks! That was it. It seems that it maybe isn’t so useful because only single rems can be referenced? Is that correct? So it would always be just one level? I may not be understanding it. Thanks again!

the | symbol represents the reference of rems that are not Top Level

If you reference a reference, you may count the pipes to see how many levels of references it has. This is mainly useful for adding slots that are references and annotating them differently from their original rem.

Are you talking about the | symbol?
You can turn it off on Settings → Labs → Include Hierarchy Info on Rem References

I see – thanks for the explanation. It is useful to know that.

Thanks UMNiK also – I have never used Slots so this is a nudge for me to read more about them.