This… is like trying to answer that age-old question of ‘what is the meaning of life?’ I don’t think there is a single, straight answer and trying to find out what constitutes a winning process for sifting through is extremely hard. Like art itself, people’s opinions based on what they observe are subjective.
The shorthand of it may well be, based on ‘critique = disciplined & systematic analysis’ and ‘criticism = judgmental / often regarded as negative’, to identify which ‘critique’ aims to be purely constructive in nature (in a not overly-judgmental way, making it instantly cater to the subjective tastes of the individual who wrote it). We’ve all heard the term ‘constructive criticism’ and that’s exactly what it is.
Criticism: “The way you’ve drawn the arm is way off the mark, it looks terrible. If the muscles were bulkier, I’d like it. As it stands it’s pretty crap.”
Critique: “It’s obvious that you’ve put a lot of time and effort into studying anatomy from what I see of your drawing. I can appreciate that it’s a hard subject to learn. To my eyes, it looks like the proportions of the arms are a little uneven, although I realise this may have been intentional (or a subject of style). If you’re interested, I know several good books on anatomy that may be of use to you, as I can see we both share this interest.”
Tactful and polite, not overly-opinionated and above all, adding something constructive, it’s obvious which one of the two examples would be the more valued. If it’s ‘crap’ (by their standards alone perchance? Do others feel the same way?), they shouldn’t just say so, they should explain why. This makes all the difference between a critique that is negative to the brink of criticism and one that points out, in the nicest possible way, what could be improved (and therefore is useful).
In short, through just changing the tone of the language we use to communicate with one another, and being a little considerate, a critique that has some negative pointers suddenly becomes more positive.
On the other hand, of course, it also has as much to do with the artist’s reaction as it does with the said critique. Are they able to take criticism with a pinch of salt? Treat it as a few helpful pointers and move on with a mind to improve for their own satisfaction more than anything else (that old chestnut that if you’re doing art for others instead of for yourself, why are you doing it at all?) Or, do they completely flip their wig and rant about it?
In the design industry (and many other creative industries I’m pretty sure), you come around to the fact that criticism comes part and parcel with the job. If you can’t accept it and act upon it professionally (it may very well add something positive after all), then you’ve chosen the wrong career. It’s always best to acknowledge whatever comes your way and, good or bad, just bear it in mind and move on.
I hope this answers your question (constructively, huzzah!), and thank you for asking such a cracking good one at that. ;)