There are some corner cases where the different solutions disagree.

The test file:

a,b,c,d,e
f,g,e,h
i,j,
l,m
n
,
[download]

greatshots' output:

a,b,c
d,e,f,g,e
h,i,j,l,m,n,
[download]

(no newline at the end)

My output:

a,b,c
d,e,f
g,e,h
i,j,l
m,n,
[download]

(no trailing newline)

ikegami's output:

a,b,c
d,e
f,g
e,h
i,j

l,m
n
,
[download]

It would be interesting to know what the desired output is (and if it matters at all)