gatsby-plugin-mdx randomly inserts non breaking spaces

Description

Some lines (text) are not properly broken up on when using MDX. This is especially annoying on mobile, where the lines will run out of the screen. When looking into the generated html, these lines have   instead of regular spaces. I can’t find anything odd or specific in our markdown that could trigger this.

Steps to reproduce

1. Clone demo: https://github.com/joeplaa/gatsby-mdx-repro-31559
2. Install and run develop
3. Browse to article “Hoeveel btw zit er op iZettle diensten?” (top of page)
4. Search for “Je zou misschien denken”
5. Open devtools in Chrome (or equivalent in other browser) and view element with text from search above. It shows it is rendered as: Je zou misschien denken dat je deze uitgaven dan helemaal niet in 

Expected result

MDX/markdown/Gatsby should not insert non breaking spaces. Instead it should only insert normal spaces.

Actual result

Multiple lines contain non breaking spaces without explicitly having typed them.

Environment

  System:
    OS: Windows 10 10.0.19042
    CPU: (8) x64 Intel(R) Xeon(R) CPU E3-1245 v3 @ 3.40GHz
  Binaries:
    Node: 12.21.0 - C:\Program Files\nodejs\node.EXE
    Yarn: 1.22.5 - C:\Program Files (x86)\Yarn\bin\yarn.CMD
    npm: 6.14.11 - C:\Program Files\nodejs\npm.CMD
  Languages:
    Python: 2.7.15 - /c/Users/Joepje/.windows-build-tools/python27/python
  Browsers:
    Edge: Spartan (44.19041.964.0), Chromium (90.0.818.66)
  npmPackages:
    gatsby: ^3.4.1 => 3.4.1 
    gatsby-plugin-mdx: ^2.5.1 => 2.5.1 
    gatsby-source-filesystem: ^3.5.0 => 3.5.0 

[umortenb]

I just had a similar problem, and noticed that content pasted to a CMS from Microsoft Word contained non breaking spaces, which look exactly the same as normal spaces, but get converted differently. They are visible through small dots when marking them in VSCode:

[joeplaa]

Thanks @umbiermann, that solved my problem too!!! We initially copied all our existing posts from WordPress to Gatsby and some of those posts were indeed originally written in Microsoft Word, which explains where those non-breaking spaces come from. Apparently WordPress is less strict when it comes to displaying them.

@LekoArts, I’ll close this issue as my problem is solved and this is not, strictly speaking, a Gatsby issue.