I found a case of leading comma (,) on a piece of relationships at bottom (publisher):

https://musicbrainz.org/release/973a3e4f-03a5-44f3-8f8b-fd614160f89b

Special Rider Music (, from 1981 to present, from 1991 to present, from 1993 to present, from 1997 to present, from 2003 to present)

It has a leading comma.
And it is missing the tracks where it applies.

Here is the content of these relationships:

• Special Rider Music (from 1991 to present) (tracks 1, 7, 9)
• Special Rider Music (from 1981 to present) (track 2)
• Special Rider Music (from 1993 to present) (tracks 3, 6)
• Special Rider Music (from 2003 to present) (track 4)
• Special Rider Music (no dates) (track 5)
• Special Rider Music (from 1997 to present) (track 10)

I don't know how it could be displayed.
Maybe it's purposely not displaying tracks because of both dates and tracks?
Maybe we should display tracks rather than dates?
I think the leading comma is due to the no dates relationship.