Mac user here. Spelling should be controlled by OS to be consistent across applications. I vote to remove Obsidian custom spell checker in the Mac version and use native one.
Creating a new topic linked back to the original feature request of custom dictionaries because I think these are actually different features.
Use case or problem
Consistent, full featured dictionaries in multiple languages provided by the OS.
Proposed solution
If the system supports and offers dictionaries Obsidian should use the system one by default.
It don’t think those are the same feature as this one, but definitely related. You could have more languages and custom dictionaries for like medicine jargons without ever using the system dictionaries or making them the default.