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I would guess that the Acehnese traffic is being routed through Medan. You can see from both the tag activity and Google Trends that 90%+ of the Indonesian activity on Steemit is from Aceh.

Not all Aceh traffic appears to go through there, some comes up directly as Aceh.

Makes sense, probably just different internet providers doing things differently. There are some users from Medan and North Sumatra as well.

I may also be relying on Google Trends too much. It seems to take about a month for it to actually reflect a new trend (charts change daily and recent data is very unreliable), so it's quite possible that interest is simply spreading across the country.