@comma{} ¶Ordinarily, a comma ‘,’ is a normal character that can be simply typed in your input where you need it.
However, Texinfo uses the comma as a special character only in one
context: to separate arguments to those Texinfo commands, such as
@node (see @node Line Requirements),
@acronym (see @acronym{acronym[, meaning]}) and @xref
(see Cross-references), as well as user-defined macros
(see Defining Macros), which take more than one argument.
Since a comma character would confuse Texinfo’s parsing for these commands, you must use the command ‘@comma{}’ instead if you want to pass an actual comma. Here are some examples:
@acronym{ABC, A Bizarre @comma{}}
@xref{Comma,, The @comma{} symbol}
@mymac{One argument@comma{} containing a comma}
Although ‘@comma{}’ can be used nearly anywhere, there is no need for it anywhere except in this unusual case.
(Incidentally, the name ‘@comma’ lacks the ‘char’ suffix used in its companion commands only for historical reasons. It didn’t seem important enough to define a synonym.)