Linters are fantastic tools to have in one’s toolbelt. You’re totally right for using it in your project. For my use case, hashing out an idea and then throw it away 10 minutes later, it doesn’t make much sense. I would spend more time keeping the linter happy than actually exploring the idea. 
I’d like to revise my original answer, though. It should have been, “No, I’m not using an external linter, but I do use whatever linter comes with the p5.js Web Editor.”