Those aren't the only options, e.g. en.wikipedia.org/wiki/Indian_numbering_system#Use_of_separat‌​ors.

ftr, i'm not necessarily advocating for an official preference. i'm just asking.

probably related: meta.stackexchange.com/questions/303120/… but I hate to say not useful (sorry Catija)

This is the canonical for spelling; meta.stackexchange.com/questions/23869/…

Not wanting to make this more complex but there are also language sites (native: ruSO, ptSO, esSO,jpSO and korean.se, italian.se, ukraine.se etc) so I guess it is hard if not unfeasible to have or even give guidance on a preferred approach for all sites, except: you're on your own.

@rene i specified English-language sites in the question. :)

Ah, yes, of course I missed that :/

@rene i've added your links and summarized their conclusions. thank you for digging those up.

i've found this question which i believe is a duplicate of my question. i've voted to close my own question as a duplicate of that one. the consensus there is "please use the US/UK style of number formatting".

@WoodrowBarlow I don't think that dupe applies here, unless I misunderstood your question. I assume you are asking about post content. That dupe you found is about the numbers the SE software itself uses to display numbers (things like reputation, people reached, viewcount etc).

@rene you're right, i didn't catch that. i'll keep my question open, then!

@RobertLongson -- that's the one rene and i were just discussing. i thought mine was a duplicate of that, but upon closer discussion it is not. i've described why in the edit.

@Ward-ReinstateMonica - no. that's the same question the previous two commenters mentioned. it isn't a duplicate and the reasoning is already included in my edit at the bottom of my question.

Canada is like US/UK, 1,000.00.

@philipxy oh really? i was going off a few vague sources online. maybe it's one of those things that's only used for government documents.

@rene Imperial! A dozen-bevybushell byte stack to recurse to a depth of four gross manyfathoms. Although that's not too different from what we still do with time.

A quick google gives a government .gc.ca style page with a footnote "the period is the generally used decimal marker" but seriously that should be "always". One might use comma or both discussing a comma locale or mixed locales. (Maybe that arises more in Canada due to bilinguality.)

@philipxy the Canadians tried to set standards on SE before: meta.stackexchange.com/a/254756/158100