I think this is what the current system is supposed to do.

That was part of the original discussion, anyway...

Here is some perl-golf code to show what I believe to be the intended functionality:

# These are the values computed elsewhere.  Change as desired to test.
+..
$REP  = -12;
$NORM = 6;
$Vote = 1; # 1 for ++, 0 for --
$XP = 0;
####

$XPChange = $Vote || -1;

%Odds =
  (0         => [ .33,  .33],
   $NORM     => [ .33,  .50],
   $NORM * 2 => [ .33,  .66],
   $NORM * 3 => [ .25,  .75],
   $NORM * 4 => [0.00, 1.00]);

$XP += $XPChange
  if rand() <= $Odds{(sort {$a <=> $b} grep {abs($REP) >= $_}
                      keys %Odds)[-1]} -> [$REP >= 0 ? $Vote : !$Vote]
+;

print $XP;
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Russ
Brainbench 'Most Valuable Professional' for Perl