=MAX(IF(ISNUMBER(FIND(",",A1:INDEX(A:A,ROW()))),ROW(A1:INDEX(A:A,ROW())),))
Instead of MATCH which looks from top to bottom and returns the first match, use MAX to return the max row number of the cell containing ,. You can use either FIND or SEARCH.
If you wrap it in INDEX you get your value:
=INDEX(A:A,MAX(IF(ISNUMBER(FIND(",",A1:INDEX(A:A,ROW()))),ROW(A1:INDEX(A:A,ROW())),)))
It might require to be entered with ctrl+shift+enter. I'm unable to test it in older Excel version.
Edit for further explanation of how it works:
A1:INDEX(A:A,ROW()) is to be read as cell A1 up to the current row in column A. So if you're at row # 10 it would equal A1:A10.
Wrapping that range in FIND returns the position of the character you try to find.
If given character is not found in the cell it returns error #N/A.
So if you have row 1 and 9 containing , in this case, it returns an array of numbers for the hits and errors for the non-hits, for instance {2,#N/A,#N/A,#N/A,#N/A,#N/A,#N/A,#N/A,6,#N/A}
Wrapping that in ISNUMBER changes the non errors to TRUE and the errors to FALSE.
IF takes that array and in case of TRUE (a number) it returns the row number (same indexed range is used).
Then MAX returns the largest row number of that array.
Instead of FIND you could also use SEARCH. FIND is case sensitive, and SEARCH isn't, further on they operate the same).
