I postulate that thread-starter had simply moved the "up" before the "come" in "come-uppance" (unfortunately, in the process, using the wrong vowel in "-commance") as a precaution, in case "up" should be construed as a preposition (even though, in this case, it was clearly not), as sort of a nod to Churchill's supposed comment on the inadvisability of ending sentences with prepositions: "This is the type of arrant pedantry up with which I will not put."
Whew! That was hard to write. Probably even harder to read. Sorry!