"I like him less than you."
Translation:Lubię go mniej niż ciebie.
Could it be 'ty' or wy as in ... i like him less than you like hime?
Hmmm... it seems that it could be interpreted this way. I don't know whether I should accept it, though. It could be harmful to some learners if they interpreted the sentence as the usual "I like him less than I like him", put "ty" anyway, and got it accepted...
This is a sentence that very well shows this "no unstressed forms of pronouns at the end of the sentence" rule (a rule that is broken by short sentences like "lubię cię").
Basically, from pairs like "mnie/mi", "jego/go", "ciebie/cię" only the stressed ones (the first one in those pairs) can usually be in the end position. So if it was "I like you more than him", that would be "Lubię cię bardziej niż jego".