Important Mistakes in Rules Design Made in the Past

General Mistakes

Using ambiguous language, terms, concepts, or translations.
Using ambiguous procedures or ambiguous purposes of phases related to transforming the game from the alternation to the scoring.
Being incomplete or surpassing the rules authors' own insight. (Note: This occurs especially frequently for descriptions of "life" and "death".)
Using superfluous concepts.
Creating contradictions or vicious circles.
Letting shape classes or the right to pass depend on qualitative analysis of arbitrarily many and undefined hypothetical-sequences and hypothetical-strategies. (Note: This is a key mistake of the Chinese 1988 Rules, the Ing 1986 Rules, the Ing 1991 Rules, the Japanese 1949 Rules, the Japanese 1989 Rules, the Korean 1992 Rules, the World Amateur Go Championship 1979 Rules, and possibly of other versions of professional rulesets never translated into English.)
Mixing rules of play and tournament rules carelessly.

Particular Mistakes

Ko Rules

Assuming that strings could be distinguished by cyclical versus non-cyclical removal. This is impossible because each string can be removed in a cycle.
Assuming strategically interesting cyclical strings consisting of at most three stones only. This is wrong because cyclical strings consisting of more than three stones are known.
Creating undecidable strategic decisions by not specifying that the result "No Result" equals the result "tie" for the purpose of making strategic decisions.

Example: Japanese 1989 Rules, Black to move:

# # # # #
. # O # .
# O . O .
O O O O O

Black cannot know whether he should create a double ko seki or a triple ko. The rules leave it unclear which, if any, is better.

Too Frequent Pass Fights

Creating frequent pass fights.

Example: Trying to simplify the American Go Association 1991 Rules by omitting the "White moves last" rule while using Territory Scoring. Black to move, no prior pass, no prior prisoner:

. # # # #
# # # . .
O O O # #
O . O O O
. O . O .

Black passes, White throws in, Black captures, White passes, Black passes is a possible perfect play move-sequence and leads to the score -2. The pass fight is about passing first in the ending succession of passes.