I've separated interfaces from their implementations by different packages, it's just add clarity, the separation is good looking and it is easier to navigate the project structure. I like it. The only point which confuses me - I've started thinking I might overdo stuff. So the question is - do you think it's a good practice to split code like that?
I think it is fine, and I do it.
However I would flip it from how you are doing it, the *impl on every class would drive me insane. Instead I would name the interfaces differently (IThing as I am .Net type) and have them in an Interfaces folder. Then the concrete class (Thing) is 'normal' and would not need to live in a concrete class folder, just wherever made sense.
In some cases I then publish the interfaces folder as a Contracts package for other things that want to work with my main types.
