Here's a brief description of the piano in question: Baby grand; goes out of tune quickly (days after tuning); strings that break frequently, which are not replaced for weeks or even longer; a squeaky damper pedal that does not lift the dampers until when pressed about a third of the way down; not to mention unbeautiful sound across all register of the keyboard.
Will it be very harmful to the student to have lessons on such a piano? I can't imagine a beginner learning on it, but I'm relatively advanced and luckily have a reasonably good piano to practice on. Will the damage be less the more advanced you are? Afterall, this is my teacher's practice piano and he regularly gives concerts.
On the other hand, unlike him, I'm far from a finished product. I'm perhaps at a stage where I need to start learning about how to produce a beautiful tone on the piano. Will this piano hinder my progress? My teacher believes in doing things by carefully listening to the sound you produce on the piano; he's not a fan of theorizing about consciously adopting certain wrist/arm movements to get certain sounds. How could I aspire to producing a better sound on a piano when I often have trouble appreciating the sound that comes out of that piano? Unfortunately, while my teacher also compalins about that piano, there is virtually no prospect of his getting a new one.