Composer's Rich Text support is broken in many ways, but it cannot be disabled

What version of the Codex App are you using (From “About Codex” dialog)?

26.715.31925

What subscription do you have?

Plus

What platform is your computer?

Microsoft Windows NT 10.0.26100 x64

What issue are you seeing?

Please see the screencast. Watch carefully, please, as it shows at least 4 different problems, all of which are caused by the poor quality of the implementation of what is apparently supposed to be Rich Text mode support.

https://github.com/user-attachments/assets/8a607fa1-4d52-4486-a007-e133b61ce3f5

Main issue:
While Rich Text mode support is broken in so many ways, it cannot be disabled.

See #33586 for additional context on how that buggy mode produces unintended input that changes code meaning, that is eventually silently sent to the model.

What steps can reproduce the bug?

Use the Codex chat UI "composer" either in VS Code or in the Codex (aka ChatGPT) App, and try these scenarios:

• Writing or pasting lines containing the - symbol at the start of the line
• Pasting code int readPointer(); from a C++ file with the Night Owl theme enabled (where readPointer is shown as italic)
• Copy a word from a line that appears as a list item inside the composer, and paste it elsewhere

Then:

• Try to locate a setting like "Plain Text mode" or "Rich Text mode" somewhere. There is no such setting, meaning that we are forced into a non-working "feature" without any chance to fully disable it until its proper implementation is landed.

What is the expected behavior?

_No response_

Additional information

This affects both: Codex (aka ChatGPT) App, and the VS Code Codex extension.