Etiquette: the customary code of polite behavior in society or among members of a particular profession or group.
Etiquette changes depending on the situation. If you are eating dinner at home with your family, it likely doesn't matter which fork you use (or if you use the same fork for everything... or at all). If you are at a formal dinner your choice of fork might be a big deal. For something non-food related an example could be that it is inappropriate to use profanity at most work places. It is not universal, but in general you shouldn't be swearing at work or in professional emails. As the definition states, it is a customary code of polite behavior. What is polite and correct for me at school is not the same as what is polite and correct at a model horse show. But there are definitely some things that are universal about etiquette. It is basically a customary code of politeness.
The Internet has done some really strange things to politeness in general. A lot of people feel quite free to just shred someone for having different views, for something they made or for no particular reason at all. We definitely see a lot of this in the model horse hobby. A new model comes out and a lot of people are really excited about it. And a lot of people have a laundry list of things they feel are wrong with the horse. Sometimes you just get a generic "it's ugly" post. It is completely OK to not like something that an artist produces, but there really is no reason to shred the piece because you don't happen to like it. I think these days a lot of people forget that there are PEOPLE behind these things that we collect. Someone sculpted the horse, painted it, made the tack, the props, etc. A person took their time and creativity to create a thing. If you don't like it, move on. If it's not how you would have done it, so what? Make your own thing. Then you can do it just how you want to.
I asked a friend of mine, who has judged model horses for years and shows her real horses in showmanship, to critique the above photo for me. She liked it, said it looks correct but she would really like to see this entry from the other side. I said to her that my thought process when I took the photo from this angle was that in photo showing, judges generally want to see the horse. From the other angle the doll is partially blocking the horse. My friend acknowledged that but said the whole photo would work better from the other side, maybe even with the judge in the extreme foreground of the picture. And I agree with that. I do still like this photo. It is a correct photo, but likely it would do better from the other side. The important thing in that story was not that I agreed with the critique, but that I asked for it. That is a basic rule of etiquette for all aspects of life. Yes, everyone has an opinion, but sometimes people just want to share a thing because they like it or because they are proud of it. They don't want to see a bunch of negative comments about why it is wrong or how it could have been better. Sometimes the entire point was to share.
Another really important piece of etiquette can actually sort of apply to other things as well. Like, don't dish it out if you can't take it. In our house we always say teasing is love. There are definitely lines that should not be crossed, but teasing, and taking the teasing in return, is often hilarious! It's a good idea to keep the idea in mind that critique is a two way street. While I was looking for another way to say "don't dish it out if you can't take it" I found a really great entry in the Urban Dictionary. It says " don't give criticism if you can't take criticism. Don't say thing's about other people if you don't like things said about yourself in return."
It is really poor form to give unasked for critiques but also to give critiques while refusing to take any for yourself. No one is perfect. Most of us know it. Critiques can absolutely be essential to growth in many aspects of life. But what if you are just starting out as an artist? Or you just learned to sew and made your first ever thing on your new machine? Or if you have worked hard on your performance entries? Or you even just wanted to show off that new Breyer you bought. Sometimes people just want to share. People are social creatures, even the most antisocial among us needs to be seen (even if they only want to be seen from a distance). Sometimes the shared thing is just that, to share.
So please try to keep in mind that when you critique without being asked, it's rude. If you critique things and then fly off the handle if anyone critiques your things, that's not cool either. And please, please remember, if you are asked to critique something remember that a person was behind creating it. A person who likely worked very hard on the thing and is likely very proud of what they did.