The decimal and thousand mark in sewiki should use the same as nowiki/nnwiki. The majority of the Sami language speakers live in Norway, Sweden and Finland and use the same written number system as other people in those areas.
There is an old note about this on the internal Signpost, but I forgot to register this on Bugzilla.
Version: unspecified
Severity: normal
CLDR agrees, though only with unconfirmed values: http://www.unicode.org/cldr/charts/by_type/patterns.numbers.html#Western_Digits_(latn)
This seems not to be active on sewiki of some reason. See edit on Signpost (Wikipedia:Gáffestohpu) http://se.wikipedia.org/wiki/Wikipedia:G%C3%A1ffestohpu#Formatnum
The fix was merged. It will become active in the next 1.21wmf1 deployment. Please test on Mediawiki master.
http://www.mediawiki.org/wiki/MediaWiki_1.21/Roadmap#Schedule_for_the_deployments has schedule for 1.12wmf10