Structural element with built-in meaning.
\[InvisibleComma] is by default not visible on display, but is interpreted on input as an ordinary comma.
\[InvisibleComma] can be used as an invisible separator between indices, as in .
See The Mathematica Book: Section 1.10.4 and Section 3.10.5.
See also: \[AlignmentMarker] , \[Null] , \[InvisibleSpace] , \[RawComma] .