As someone who's worked on this, I'm oh so conflicted. Yes, it's mostly a terrible idea, if CodeMirror and the likes work. On the other hand, there's so much default behaviour that's just excellent that'd need to be reimplemented if you started from scratch. It can't be denied that contentEditables have the advantage of just requiring much less code overall.
To this extent, I've written a hook for React/Preact that attempts to be a decent code editor basis on contentEditables: https://github.com/kitten/use-editable
Funnily enough, if you just search the code for "// Quirk" it's easy to see that this experience wasn't pleasant in the slightest. But it did allow me to write a code editor in just about a day which can be found here: https://trygql.formidable.dev/
I'd say, there's plenty of edge cases to take care of. But on the other hand, things like composition, selection behaviour, and other niceties are things that you just have to take care of much less
To this extent, I've written a hook for React/Preact that attempts to be a decent code editor basis on contentEditables: https://github.com/kitten/use-editable
Funnily enough, if you just search the code for "// Quirk" it's easy to see that this experience wasn't pleasant in the slightest. But it did allow me to write a code editor in just about a day which can be found here: https://trygql.formidable.dev/
I'd say, there's plenty of edge cases to take care of. But on the other hand, things like composition, selection behaviour, and other niceties are things that you just have to take care of much less