As the one who started the "throw-out" question a year ago, I find it funny to be the "poster child" now.
The original proposal was simple - if there were N autocrosses, everyone just gets their N-1 best scores. If you missed one event, you had a zero that got thrown out. If you attended all, but there was a rain-out, you had a 5 that got thrown out. If you attended all and there were no rain-outs, your lowest finishing score was thrown out.
This allowed participants to miss one event without being completely knocked out of a close competition. With that scoring, I would throw out a 5, leaving 90 and Charlie would throw out a 0, leaving 85.
As several people pointed out, the rain-outs mess up this simple scheme - but, since people paid good money to attend, some points for a rain-out seem fairer than "thanks for the money, no points".
One of the factors no one has mentioned is the disproportionate effects of the place scores - why 20, 15, 12, 10, 8, etc? If only two people show up, they finish with 20 and 15 points respectively for that day.
In sailboat racing, scoring is much simpler (and fairer?) by just eliminating "bonuses" for finishing places. The usual scoring method (there are variants) is as follows:
Each person scores their finishing place (1st = 1 point, 2nd = 2 points, etc.), and the winner of a series is the person with the lowest overall score. If someone attends, but is unable to complete a given race (DNF), they score the number of actual "finishers" in that race, plus one point. If someone misses a given race completely (DNR), they score the number of actual participants, plus one point. This way, someone can miss a race with four entrants and only score as though they had a fifth place finish, whereas in our scoring scheme, it is as though you finished 12th (or worse), even if only two showed up. In the case of a complete race cancellation (i.e., a rain-out), everyone present would just score the number of actual attendees, and those not present would score that count plus one. There are usually one (or even two) throw-outs as well, to allow a missed event. (To clarify the DNF/DNR situation, if 4 people show up, but 2 break down and cannot finish, you have a 1st, 2nd, and a 2-way tie for 3rd, and anyone who didn't show scores as though they got a 5th.)
This way, your points are driven by how you actually placed
in competition - you don't get a huge bonus just because your strongest competitor didn't show up.
Note that there is NO way to completely, fairly, do scoring that handles missing one or more events. Even the sailing scoring would leave me with a couple of point advantage and Charlie would have to beat me in the last event by at least 3 places to win overall honors.
I would suggest we either:
A) Go with the N-1 scoring (best N-1 scores of N events are used, rain-outs are included), or
B) Have no throw-outs