Merriam Webster Learning Dictionary: Feedback: Helpful information or critism that is given to someone to say what can be done to improve a performance, product etc. Critisim: The act of expressing disapproval and of noting the problems or faults of a person or thing. Opinion: A belief, judgement or way of thinking about something, what someone thinks about a particular thing. So, when you say something sucks and leave it at that, you are merely giving an opnion. At least have the common decency to say why something sucks and even give an example or two. "Hey so and so, a spellchecker would go a long way to making this story better". They are asking for feedback afterall, not opinions.
You never said what feedback is not. Btw, yes feedback is an opinion; and that is what you are supposed to do with the feedback button. Not spam pointless questions to our developers.