Which manual of style suggests using parentheses within parentheses?

Question

When it comes to nested parentheses, there are two options. (The first is to use square brackets for the inner text [like this]. The second is to simply use parentheses (like this).)

I believe that nested parentheses should be avoided where possible. But in case they are inevitable, I can see a drawback to both approaches. Using square brackets might be confusing since they are more commonly used for other purposes, while using nested parentheses can be confusing since the reader might have a hard time keeping track of which parentheses were closed.

APA suggests using square brackets for the inner text. The Chicago Manual of Style also suggests this, but it seems that it also mentions that

British style is to use parentheses within parentheses.

I also found this guide, which suggests that UK English uses parentheses throughout.

So my question is, which British manual of style suggests using nested parentheses? I found some British manuals of style that I could check, like “New Hart’s Rules: The Handbook of Style for Writers and Editors”, however, it seems that they are not freely accessible online.

Answer 1

I was able to find 3 publicly available British manuals of style which mention nested parentheses.

1. British Chicago Footnotes Referencing Guide

This is a guide for referencing using footnotes, as opposed to a general style guide. However, it briefly mentions nested parentheses:

The entire source need not be put in parentheses, which involves changing existing parentheses to brackets and creating unnecessary clutter.

This suggests that parentheses are expected to be changed to brackets when they are nested.

2. GOV.UK Style Guide

In the “Brackets” section, the following is specified:

Use (round brackets), not [square brackets]. The only acceptable use of square brackets is for explanatory notes in reported speech:

“Thank you [Foreign Minister] Mr Smith.”

Therefore, this style guide would use parentheses within parentheses.

3. European Commission English Style Guide

While this isn’t strictly a “British” style guide, I am including it since it mentions the following.

For reasons of stylistic consistency, the variety of English on which this Guide bases its instructions and advice is the standard usage of Britain and Ireland.

In the “Brackets” section, we have the following:

A second set of round brackets (not square brackets) can be used to set off text that itself contains text in brackets:

The conclusions of the analysis (in particular regarding fair trade, the environment and transport (including green cars)) highlighted the following:

However, to avoid confusion, it may be better to use dashes (see 2.16):

The conclusions of the analysis – in particular regarding fair trade, the environment and transport (including green cars) – highlighted the following:

Summary

I found 2 style guides that would use nested parentheses: The GOV.UK Style Guide and the European Commission English Style Guide (although the latter recommends using dashes if possible, in order to avoid confusion).