Then prepare to have your mind blown (if you haven't heard about this before): the correct culture-agnostic term is "grouping separator" because not everyone uses 3 digit groups - in some East Asian languages (specifically Japan and China, not sure who else) you have separate words for "ten thousand" and use 4 digit groups.

Don't you find exponent notation to be neater?

1E+03 = one thousand 1E+06 = one million 1E+09 = a thousand millions / an american billion 1E+12 = an american trillion / an european billion

.. and that's as far as you need; the GDP of most countries is on the order of 1E+12 or 1E+13

I think I have genuinely never seen scientific notation used in an accouting context. If it can be rounded, then we will use 1MM or 1B.

I see it as follows. Unlike science, where there are a few numbers related in complex ways, accounting has very many numbers, related in very simple ways.

I assume he requires a few more significant figures in his line of work

It's not like scientific notation precludes that. 1.234567E+06 = 1234567, but it's also at a glance obviously around 1 million

wait wait wait, a billion means two different things in Europe and America? I'm from Europe and I always used 1 billion to say 10^9. I hardly see how I would not have noticed figures being so different in say, news articles from America and Britain.

When I was growing up in Ireland, a billion was a million million in Britain and Ireland. Now, we have adopted the American thousand million. In Germany and Italy, a thousand million is a Milliard, and a billion is a trillion.

Slovak and Czech have it same as Germany/Italy.

Yes, they are. I just prefer to use space for this.

A space is a pain to transmit between umpteen file formats.