Reply #7, 8th overall. Made in reply to post #4.
I think I understand how the Sort by Topic option works. It has nothing to do with the Subject line. Instead, when Sort by Topic is chosen, the individual posts are ordered based on the post from which each was a Reply. If two people reply (posts B & C) to the original post (post A) directly, and then another replies to the first reply (post D), when Sort by Topic is selected, the order will be
A
B
D
C
since D was made in reply to B.
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