This is a small thing, but during page proofs for a paper we were requested to format numbers as having no commas unless they were 5 digits. That is, 4000 vs. 4,000. But to include a comma if the value is 10,000 but not 9999.

The table in question (that had the offending numbers) was a flextable. It turns out that, as with most things R, there is a solution. The flextable package has a function colformat_num() for this purpose. Here you can use various options used in the format() base function including the use of big.mark. The big mark is what character to use (often a . or ,) to separate 10^3 values.

Fortunately, I had only one 4-digit number to deal with (e.g., setting big.mark=''). It would not have been as obvious how to implement the markup needed in general.