Even this pedant (myself) often does not fill in all of the dame when playing with Japanese rules on OGS. In most cases, my opponents indicate a laziness to fill out the remaining dame (by passing early), so I simply pass as well, and we score while assuming that the dame had been filled.
I’ve written about dame filling in other posts:
The Japanese rules technically imply that dame need to be filled in order to prevent “normal” living groups from being consider in seki, which would nullify their territory.
Filling dame appears to be the practice in at least some formal, professional situations (as seen in the video that @smurph linked above). Note that filling the dame also aids with their counting procedure, making it easier to rearrange territory into rectangular regions without worrying about accidentally counting dame.
O…
Compulsory Dame Filling to Prevent Technical Sekis
In Japanese rules, eyes of groups in seki do not count as territory. This quirk of the Japanese rules could possibly be a holdover from the group tax effect of stone scoring rules, a historical forebear of the Japanese rules, (see this post in Pondering Upon The Rules Of Go which also links to an article discussing the history of the rules of go), although certainty of its origin is likely lost to history.
However, this rule is loaded with comp…
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