pioneerspacesim/pioneer — pull request #2819 by impaktor (2014-03-20 08:18:01+00:00)
Title: start grouping digits from some number

What should default be for English? Grouping starting with 1,000 or 10,000?
[wiki](https://en.wikipedia.org/wiki/Thousands_separator#Exceptions_to_digit_grouping) says:

The International Bureau of Weights and Measures states that "when there
are only four digits before or after the decimal marker, it is customary
not to use a space to isolate a single digit".[13] Likewise, some manuals
of style state that thousands separators should not be used in normal text
for numbers from 1000 to 9999 inclusive where no decimal fractional part
is shown (in other words, for four-digit whole numbers), whereas others
use thousands separators, and others use both. For example, APA style
stipulates a thousands separator for "most figures of 1,000 or more"
except for page numbers, binary digits, temperatures, etc.

so I assume no grouping for `< 10,000`.