Reverse Komi
Komi given to Black, the starting player or the player receiving a handicap.
Robert Pauli: Instead of speaking of reverse komi one can also allow the value of (normal) komi to drop below zero, e.g.
- 6 points reverse komi = -6 points (negative) komi
To give Black 6 points is, of course, the same as "giving" White -6 points (I know I'm being silly here).
Now that we allow the full range, it would be more logical to turn the sign of komi (at least in my opinion). To increase a handicap would then either increase the number of handicap stones or increase the komi (or increase both).
But, of course, we're used to even games played with 5.5 komi or the Nihon Ki-in increased komi to 6.5, so it seems easier to keep it this way.
- For an example of negative komi at pro level see Amateur Honinbo vs Pro Honinbo 2002.
- For an example of the organized use of negative komi in Japan see Point Ranking Scheme At Tokyo Go clubs.
Andre Engels: Negative komi is mostly used at smaller board sizes, because a more fine-grained difference is needed - between two players n stones on 9x9 might be clearly better than 50% winning for White, but n+1 clearly offer better chances for Black. Depending on the more exact differences, they could then play n+1 stones with komi for White or n stones with reverse komi.
Robert Pauli: Actually, negative komi should be used on the 19x19 as well, Andre. In fact, every handicap game should have negative komi - provided the ranks are one stone apart and handicap stones lack synergy (behave linear):
gap = 0 -> "handicap" 0.5 = place 0 and receive 6 (i.e. give -6) gap = 1 -> handicap 1.5 = place 1 and receive 6 gap = 2 -> handicap 2.5 = place 2 and receive 6 ...
Andy: I'm not a big fan of reverse komi. It is possible for the weaker player to blunder away stones and territory, but the reverse komi never goes away, even against perfect play.
RiffRaff: I think that's at least partially the idea. I've heard some stronger players mention that they like to play with reverse komi instead of handicap stones when they want to work on their Fuseki. Besides, even Go Seigen used it in playing against amateurs: http://www.gogod.demon.co.uk/NewInGo/19800720_1.htm.