I think it’s important to look at this from three distinct sides:
Collector: They want what they like, and comment primarily on things that match what they have decided to pay money for in the past or those pieces that in some way stray from what they believe to be "good" design or materials. The value of their collection is either internal (personal taste, satisfaction) or based largely on their perceived resale value if the collector follows that part of the hobby, or a combination of both. Collectors are the only experts on their own personal likes and dislikes, and should freely share those likes and dislikes with dealers and makers. Some have additional knowledge of knife making techniques and market trends, but that knowledge is usually limited again to their own tastes. A collector focused on forged knives might not be an expert on highly technical stock removal makers and a collector who likes CNC milled folders might not be an expert on normalizing cycles or hamons.
Dealer: They want what their customers want, which can align or not with their own personal tastes. Their livelihood depends on them representing either a collection of makers or knives wide enough to suit all collectors or specific enough to suit a particular niche of collectors upon which they focus. They are the experts on the market, trends, and sale and resale values.
Maker: They make what they like, with a proper eye on the market as a whole. Some cater to particular collectors, groups, dealers or even dedicate their work to a particular style or time period. Makers are the only true experts on knifemaking, but are not necessarily experts on what will sell well, how to sell knives, or market trends.
How I see this situation is that:
-Collectors need to realize and act knowing that much of what they offer for feedback is opinion or taste and comments should be given/taken as such. $100,000 in knife purchases does not make a collector an expert on knives (other than the ones they own), knifemaking, or market trends. It makes them a person who is serious about their collecting and has funds to support the collecting. By nature, collectors who spend more money tend to know more about some aspects of the making process, but usually in order to be more knowledgeable when making higher-end purchases. This is not to say that a collector cannot become an expert on knifemaking or knives in general, but that knowledge is not purchased when you buy a knife. I think that if you are highly educated on aspects of knifemaking, design, and implementation, the fact that you are a collector should not even factor into critique as it shouldn’t matter what you collect in order to properly measure a knife's place. Opinion and critique are two different things to me, and response to a picture needs to be an opinion, a design/implementation critique, or a blend of the two done in a way that each part is clearly defined. I think the problems are when someone spends 20K on knives and thinks they are now an expert on knives or knifemaking simply because they own works made by mastersmiths. I can buy a Rolex but it doesn’t make me an expert on the internal workings of wristwatches unless I do a LOT of homework, and only then should I be commenting on how great the gears are and why.
-Dealers seem to be doing fine and don't often comment here outside the makers they work with. They account for most of the only real "business" aspect to knifemakers, as most knifemakers would admit that the "business" side is almost always the most foreign to a maker. Additionally, they act like businessmen and won't often post their negative opinions on things because it would be bad business to do so. You never know who will develop into a MS some day and not work with you because you were a jerk when they were on year 1.
-Makers need to realize that any picture of their knives posted on a public forum is an open invitiation to anyone who sees it to chime in with their opinion. Makers also need to realize that although anyone can comment, the value of those comments is something only the maker can truely weigh. That being said, makers also need to realize that posting pictures with flaws may also HURT their business and need to decide if that risk is worth it to them. In-person verbal critique has the advantage that no one else needs to hear it. 10,000 people seeing an outspoken collector voicing his distaste for a knife doesnt do much to help that maker sell that knife or future knives, regardless of if that collector's comment is valid in any way.
Lastly, makers need to suck it up a little and stand up for themselves as they are the true experts on the knives they make. Collectors aren't the only ones whose opinions matter. This is a business. If someone came into a custom car shop and started telling them about all the things they didn't like about their cars and offered no actualy feedback beyond "i dont like chrome the way you use it and dont like embroidrered seats and don't like the dual exhaust you guys use," the shop's response would likely be that the opinionated consumer could go ahead and leave, because thats what they choose to work with. They might not sell that one guy a car, but why would they want to work with a collector who obviously would be better suited with another shop, and less hassle. There comes a time when you need to decide if youre trying to please everyone, mostly everyone, or a few very specific people. Once you've made that decision, its much easier to discount opinions that differ from yours on knife design.
The toughest part? The opinions of the collectors drive the business of the dealers and the sales of the makers. Collectors wouldn't exist without the makers, but the makers wouldnt exist without the dealers and collectors, and the dealers wouldnt exist without both makers producing and collectors buying. Where critique factors into that complex ewuation, i have no idea. My guess is somewhere in the realm where makers are looking find out where they "fit" and collectors are trying to have more knives put into the "pool" from which they purchase that also have the characteristics that they personally look for. I've yet to see a collector offer advice to a maker on how to make a knife better for his intended audience, rather than that specific collector as the potential purchaser.