For me, this is really a pretty simple thing. If a maker posts his work, he opens the door as they say in the courtroom, because the post really is a: "Look what I just made, what do you think" sort of post, even absent words to that effect, and the maker is taking a
calculated risk with a possible commercial payoff, so he assumes the risk of getting some negative comments and must at least tolerate them if he wants the possible payoff (new orders, prestige), it's
fair.
But, when a collector posts his newest toy, I believe the right thing to do is praise, or keep silent. Collectors rarely if ever post pics of their new knives looking for criticism and it sure does take the wind from their sails if responses make them feel badly about their purchase, it's just not very nice to do, after all, isn't posting your newest knife a big, and enjoyable part of collecting? Why would anyone want to upset, and potentially turn off a fellow collector, outside of ego?
Yes, forums like this one can be useful to create growth, both of makers and collectors, but, when a collector just bought a new knife, wants to show it off, that is not the time for growth/criticism, it's the time for sharing his joy with him, or, if you don't want to, fine, but don't ruin or taint his moment because you feel it's your duty to do so. Is it duty, or ego in such cases?
There's a word that describes the idea of helping people who don't want your help, it's called
tyranny.
Just my opinion of course.