I have heard "I miss you" said like "Li manco"
Is that right?
Beacause I have also heard it said "Mi Manchi"
Which one is better/proper?
Wolverine,Properly I miss you is Mi manchi.
For example for give a more strong romantic effect you could say..
I miss you.. like (something)
I miss you like the air that i breathe (come l'aria che respiro)..
or you can explain completely your feeling. Sometimes it's better.
Less complications and less misunderstooding.
I've never heard 'Li manco'.
You can say:
mi manchi = I miss you
mi mancate= I miss you (guys)
lei mi manca molto = I miss her a lot
ti manco = you miss me
ti manco? = do you miss me?
And so on..