What do you think about coownership? I've really never understood why it was allowed.
It's dodgy as fuck IMO, simple as that.
It can often be fairer process than loaning players. I think. It's usually used in a very similar manner anyway, but makes for shared problems and benefits for both clubs. But it still seems weird.
http://juventiknows.com/co-ownership-in-italian-football-explanations-examples/
This explains it quite well if you can be arsed.