I am seeing several answers that boil down to "I do not know your answer, you should consult a vet". The goal of this SE is to help answer questions about pets. If the question truly requires a vet to answer it, then perhaps the question should be closed with out answer. In addition, hopefully we will have some vets in our community which will be able to provide better answers.
So are answers where the response to the primary question is "consult a vet" appropriate?
I'd say we need to distinguish between answers where "consult a vet" is the right response, and ones where some users will suggest that in place of a "proper" answer.
"Consult a vet" is generally very good (and safe!) advice, but frequently it isn't mutually exclusive to an answer providing high-quality advice.
For example, What's the best way to heal a scab on top of my dog's head? could very easily be dismissed with "consult a vet", yet the two answers provide what seems to be good advice (and one answer also includes the phrase "consult your vet").
Questions like this, where there is a known issue, even if it is medical in nature, are generally fine.
However, questions which attempt to diagnose a medical problem are much more problematic.
I think questions like this one about identifying spots on a cat's chin, What can I do about the black dots on my cat's chin? are perfectly fine for our site.
On the other hand, if a question seems to be asking for help in identifying a serious injury or illness (e.g. "I think my dog's leg is broken; how can I tell?" or "My cat hasn't eaten or drank water in 3 days... what is wrong with her?"), then those questions should be closed and a comment left directing the OP to a veterinarian.
If your answer consists only of "consult your vet" advice, this should be a comment, not an answer. An answer needs more information than that. (A valid answer, however, can certainly include "consult your vet" along with more information.) If it is not likely that anyone will be able to answer a question with more than a simple "consult your vet" comment, then the question should be closed.
It is only appropriate if you can adequately explain why the answer can only be obtained through a visit to the vet.
For instance if to find the answer will require lab tests, x-rays, and/or other complex medical procedures that should be explained. If you are not able to say what will be required to answer it then it is much better if you leave the question unanswered so that those who do know can answer.
Many times the first answers in if they sound about right will get voted up and drown out responses that come after. If you can not provide a quality answer that adequately explains the situation then leaving the question unanswered lets the experts focus on those questions to help resolve the problem.
In addition people are coming here many times hoping to avoid a vet bill but still take care of their animal. If all they here is a vet can answer that, they will tune it out. If you explain why they need to go to a vet they are more likely to take them to a vet so they can get the care they need.
And finally there are many things being referred to vets that do not really need to go to the vet. Many of the experts here have the knowledge of either how to answer, or where to get the answer from. Everyone knows they can go ask the vet, but running to the vet for every little question is not only expensive it is wasteful. It is similar to running to the ER every bump, scrape, or splinter. We should try to help where we can.
Here is a perfect example:
In this version it basically just says you need to see a vet.
In this version it explains why you need to see a vet.
The first version was really noise where the second one brought the explanation home which should be much more helpful to the OP.
I really wish this urban myth would die... they are not going to lose their licence for answering questions. They might is they say i am a vet and here is what you do to perform surgery, make medicine, or other dangerous activity.