Me finding out Switzerland uses apostrophes as thousands separators:  

1'341'521,49
instead of
1,341,521.49
@jbauer i was in the same way puzzled when i found out about the comma way 🤷‍♂️ 😂
btw: we do use a dot for cents aka rappen, the comma for cents is german-style ;)
@jbauer it's worse when they're like 5.000,0
@jbauer I prefer 1`000`000.00 style. The commas get confused with list separators.
@sjb Heresy!

The best way is 1 000 000.00 :P
@jbauer Spaces and commas are commonly used to separate lists of numbers. I really want a separate symbol purposely designed for separating digit blocks.
@sjb If it's a list it should use commas. The way I'm advocating for would look like:

A list of numbers could be: 1, 2000, 40 000, 532 313.46.
@jbauer I use this character
https://en.wikipedia.org/wiki/Thin_space
...to separate numbers and units (5mm/5 mm) in papers. Perhaps thin spaces would look good as digit group separators too.
Thin space - Wikipedia

@sjb Yes, that's what some standards boards advocate for but it can be difficult or annoying to type normally when on a computer (plus, who would want to write   every time in a web document).

When writing I think a thin space would work well

@jbauer I wondered how Wikipedia does it and 6.62607015 is written as:

6.626<span style="margin-left:.25em;">070</span><span style="margin-left:.25em;">15</span>

So that magically when you cut and paste the value, the separators disappear!

@sjb That is both a cool way of doing it and also incredibly disturbing from an HTML standpoint :D
@jbauer I'd have at least done <span class="digitgroup">
@jbauer yo, we do *not* use comma as a decimal separator!