Hi @fabiopettinati,
Looking at the p5-web-editor
code, I found that they use CodeMirror which is a code editor written in JavaScript.
For the private fields, looks like the issue has already been solved in 2020 on their GitHub repository:
The thing is that p5-web-editor
uses codemirror ^5.62.0
which may not be up to date with the latest package.
As @mnse said, you can open an issue on the p5 editor repository. 
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