I would never tell my student that something they did was "well done". The term "well done" refers to an overcooked piece of meat. I would also never tell my student that they will improve with practice. How can they improve if no one demonstrates correct usage and pronunciation or is willing to work with them?
@Heinz, I mean what feature in italki you have not used.
I don't know what you are referring to by "touch".
I would never make someone look stupid or uncomfortable that is learning a new language. On the contrary, I'm always trying to encourage students and cast a positive spin.