Here is a solution that doesn't make the comma globally active:
\documentclass{article}
\newcommand{\splitatcommas}[1]{%
\begingroup
\begingroup\lccode`~=`, \lowercase{\endgroup
\edef~{\mathchar\the\mathcode`, \penalty0 \noexpand\hspace{0pt plus 1em}}%
}\mathcode`,="8000 #1%
\endgroup
}
\begin{document}
\setlength{\lineskiplimit}{2pt}\setlength{\lineskip}{3pt} % for this particular case
$\splitatcommas{
\frac{1}{2},\frac{3}{5},\frac{8}{13},\frac{21}{34},\frac{55}{89},
\frac{144}{233},\frac{377}{610},\frac{987}{1597},\frac{2584}{4181},
\frac{6765}{10946},\frac{17711}{28657},\frac{46368}{75025},
\frac{121393}{196418},\frac{317811}{514229},\frac{832040}{1346269},
\frac{2178309}{3524578},\frac{5702887}{9227465},
\frac{14930352}{24157817},\frac{39088169}{63245986},\frac{102334155}{165580141}
}$
\end{document}
The setting of \lineskiplimit
and \lineskip
are for the particular case where fractions are needed in the argument.

A variant that allows nesting:
\documentclass{article}
\newcommand{\splitatcommas}[1]{%
\begingroup
\ifnum\mathcode`,="8000
\else
\begingroup\lccode`~=`, \lowercase{\endgroup
\edef~{\mathchar\the\mathcode`, \penalty0 \noexpand\hspace{0pt plus 1em}}%
}\mathcode`,="8000
\fi
#1%
\endgroup
}
\newcommand{\tuple}[1]{(\splitatcommas{#1})}
\newcommand{\set}[1]{\{\splitatcommas{#1}\}}
\begin{document}
\setlength{\lineskiplimit}{2pt}\setlength{\lineskip}{3pt} % for this particular case
$\splitatcommas{
\frac{1}{2},\frac{3}{5},\frac{8}{13},\frac{21}{34},\frac{55}{89},
\frac{144}{233},\frac{377}{610},\frac{987}{1597},\frac{2584}{4181},
\frac{6765}{10946},\frac{17711}{28657},\frac{46368}{75025},
\frac{121393}{196418},\frac{317811}{514229},\frac{832040}{1346269},
\frac{2178309}{3524578},\frac{5702887}{9227465},
\frac{14930352}{24157817},\frac{39088169}{63245986},\frac{102334155}{165580141}
}$
$\set{
\tuple{a,b,c,d},\tuple{1,2,3,4,5,6},\tuple{11,22,33,44,55,66,77,88},
\tuple{a,b,c,d},\tuple{1,2,3,4,5,6},\tuple{11,22,33,44,55,66,77,88},
\tuple{a,b,c,d},\tuple{1,2,3,4,5,6},\tuple{11,22,33,44,55,66,77,88},
\tuple{a,b,c,d},\tuple{1,2,3,4,5,6},\tuple{11,22,33,44,55,66,77,88}
}$
\end{document}

\mathbin{,}
or\mathrel{,}
. For instance,$stuff \mathrel{,} morestuff$
will allow the linebreak between the two stuffs.