Spellchecker in Jetbrains IDEs is terrible. It throws a lot of false positives.

It's pretty good imo. It's super easy to add words too, easier in fact than the spell checker in iOS or macOS. The one in iOS is the worst imo, as it adds stuff automatically based on common mistakes you make because "machine learning" and you can't even see the list of the "learned" words to remove things it learned that aren't actually words!