# Ways to indicate decimal and thousands demarkations? Possible personal “best practice” to adopt?

I've seen a few situations where the different ways to write numbers with more than three digits has become a small topic of discussion itself within comments.

1. One case is the use of a period versus a comma as a demarkation between the whole number and decimals. For example pi could be written either as 3.142 or 3,142 depending on where in the world the author has studied.

2. Similarly, An Astronomical Unit is exactly 149597870700 meters. I'd write that as 149,597,870,700 meters, but it's written in Wikipedia as using thin spaces in lieu of comma delimiters.

What are all of the acceptable ways to do this here, and if possible what might a good set of personal options be for me to adopt to be the most user-friendly to the widest variety of international readers here?

I've been using the HTML character entity &thinsp; to produce a thin space (e.g., 10 000). HTML character entities work in Stack Exchange questions and answers, but not in comments. However, it seems that browsers treat &thinsp as a breakable space, so you might end up with 10
000 if you're unlucky. There is a non-breaking thin space, which you can get with &#8239; (e.g., 10 000), but that's kinda hard to remember... The character entity &numsp; is non-breaking, but it's a full-width space, which isn't appropriate for this usage.
• I've used the "fancy, hard-to-remember, non-breaking" thin space &#8239 here and nothing blew up! Thank you. – uhoh Dec 31 '18 at 1:33