Symptom
My Mac suddenly shows double quote character " when I type option+u in VS code
to switch words to upper case.
Reason
English keyboard includes special character set.
Solution
Remove English keyboard and add Unicode Hex Input keyboard instead.
Reference
https://stackoverflow.com/questions/60870113/mac-generating-∆˚¬-characters-instead-of-executing-vscode-shortcuts-that-involve
How