In OS X Finder there is 'Comment' file property. It can be checked in finder by adding 'Comment' column or edited/checked after right clicking on file or folder and selecting 'Get info'.
How to read this value in swift or objective-c?
I checked already NSURL and none of them seems to be the right ones
Do not use the low-level extended attributes API to read Spotlight metadata. There's a proper Spotlight API for that. (It's called the File Metadata API.) Not only is it a pain in the neck, there's no guarantee that Apple will keep using the same extended attribute to store this information.
Use MDItemCreateWithURL() to create an MDItem for the file. Use MDItemCopyAttribute() with kMDItemFinderComment to obtain the Finder comment for the item.