Issue:
When using the ›World-Ready Composer‹, the character ›Nonbreaking Space‹ (^S) behaves exactly like the character ›Nonbreaking Space (Fixed Width)‹ (^s); i.e.: in justified paragraphs, its width does not adjust (like regular spaces do), but it is fixed and unchanging.
This only occurs with the ›Adobe World-Ready Composer‹ (both ›Paragraph‹ and ›Single-line‹) and not with the regular ›Adobe Composer‹ (neither ›Paragraph‹ nor ›Single-line‹).
It is not related to the font used, it has been tested with many different fonts.

1. Versions with this bug, tested and confirmed by myself or colleagues:
   InDesign (Standard Version) CS6, CC2015.0
   InDesign (Middle Eastern Version) CC2020 (15.1.2), CC2021 (16.0)
   I suppose it occurs in all versions since CS6 (when the ›World-Ready Composer‹ was first introduced, afaik)!

2. Steps to reproduce this issue
   Enter a few lines of text and insert the character ›Nonbreaking Space‹ somewhere. Choose any of the ›Justify‹ paragraph styles and select the ›World-Ready Composer‹. Switch to the regular ›Adobe Composer‹ with the same setup and compare the result.

3. Expected Result:
   The ›Nonbreaking Space‹ should adjust its width just like any other of the regular spaces.

4. Actual Result:
   The ›Nonbreaking Space‹ does not adjust its width.

5. Example as Screenshot attached.
   (Menu is in German: ›Globaler Adobe-Absatzsetzer‹ = ›Adobe World-Ready Composer‹; ›Adobe-Absatzsetzer‹ = ›Adobe Composer‹)

As far as I know, this issue has been reported only once before (https://indesign.uservoice.com/forums/601180-adobe-indesign-bugs/suggestions/39403822-non-breaking-space-is-smaller-than-regular-space-w). But in this report, it is stated incorrectly that the Nonbreaking Space would be smaller than a regular space. It can, in fact, be larger as well (e.g. in a tight line with regular spaces smaller than their 100% optimum). The real nature of the issue is that it does not vary its size.

PLEASE FIX ASAP!
Thanks