Tricky. The selection committee may refrain from telling you anything very specific about your case, because if they don't walk carefully and say something dumb, there can be a lawsuit. So, mostly you'd get some cookie cutter responses such as "it's not a good fit" or "the selection process was highly competitive" or something like that.
To soften them, I'd suggest sending the chair of the committee an e-mail thanking for their time to evaluate your case. Express a reasonable amount of sorrow but show a strong will to pursue this degree or career. Propose an informal meeting or a phone conversation to lessen their stress of crafting a written response (stress "informal"). Schedule a time, and meet or call. In the communication, never ask why you were not selected. Twist the question a bit by asking what are the traits they value in this field/industry, and in light of your application, how you can enhance your portfolio so that you can become a stronger candidate in the general pool.
Also, one school's rejects can be another school's successful candidates. On top of this very institute, you should talk to other institutes or at least attend their open day as well. The comments of the committee of the next school you'll apply probably matter a lot more.