Not specifically about UKMIL...
Maybe it's just a different world, but having known some of those who have left over the years, I get the impression it's not about being criticized per se, but the balance that isn't there, nor is there the politeness.
There is a feeling that this being the internet, "I can say anything, and screw anyone who doesn't like it", a tendency to type before thinking, to press "send" before re-reading, and think that negative criticism will be taken positively because "that's how I intended it". However, in the anonymity of the internet we don't have to look someone in the eye when we tear down their work.
How often we've seen the comments, the gripes and yes, the well-meaning descriptions of flaws or oversights, and so often without a compensatory: "Thanks for the hours of work, the research and the desire to share, but..."
Even if you don't like it, honour the effort before the tirade or the picking of nits and maybe it will be taken in the spirit intended, but a hundred negative posts (anywhere) without the appreciation is most likely to offend/annoy/discourage. We've also seen that if a person defends their work they get told to 'get with the program' and 'come up to standards', or learn what your "customers" want and bloody well produce it (even, sadly on SOH). So what options do you have.. ignore the b*&chy comments and miss the good ones? Put up with flak from those who cannot, or will not do better? Or simply go and build model boats and live quietly...
Rob