Correct!
This is true for not just mobile devices, but also desktop OSes. For example, Windows has an event, WM_CLIPBOARDUPDATE, that any application can register for. As far as I can tell, most OSes are not designed to protect the clipboard from casual monitoring
Keys should never be stored in any application or functions of a OS. Only safe place are trusted hardware wallets...
I think apps in Windows Phone are isolated and locked from each other.
The Clipboard should be one of the most secure features of any OS. This just shows me we're all still living in the 20th century.
Also... who's going to insert a 50 character long key, every time they log into SteemIt? Do you actually know anyone that does that?
In theory, you might use the embedded secure element that most modern phones have. This is a dedicated hardware chip for secure storage of keys and cryptographic operations
I have never heard of such thing.