If you ask someone about a thing or practice, or even your thing that you made yourself, and the comment that comes back is "that thing is not period" or "there is no evidence for a thing", that is not an attack. It is not an insult. Rather, it is a statement of fact given in reply to a question that was asked or as part of an ongoing conversation over a thing. There is no need here for defensiveness, though it is certainly ok to ask for sources or to engage in deeper discussion.
Further, it does not mean that that thing is unwelcome in the SCA or that you cannot choose to craft that thing that you happen to love. I can certainly discuss the absolutely complete lack of evidence for large scale Celtic art applique on Norse dress while appreciating the beauty of the item in question. I also often state that they indeed a very lovely way to approach SCA heraldry for any kit, especially for our Royals. That those things can be admired, however, does not give them historical validity, and there is nothing at all wrong with conversations that flow in that direction. Far better that someone who prefers to choose authenticity know the reality of something before they dive in and spend time and money on a project that they might later regret because it is not what they thought it was.
There are constant conversations online (and occasionally in person) about how someone destroyed someone's soul by giving comments that where not asked for. Understand that this also works both ways. If you ask for comments on a thing, you might well get some you did not expect, or some that match your own ideas on a thing. That is OK. That SHOULD be why the question was asked at the outset (to learn more). If you really do not want to know more, do not ask. To jump on the defensive over a statement of fact (that came in response to a question or as part of a conversation) can be just as hurtful, and just as game destroying, to the person who tried, to the best of their ability, to answer the question you ask. This person is taking their time to engage in a dialog that you initiated, to offer advice, to give their perspective.
Is the advice or commentary sometimes contrary to what we thought we knew? Does this shake our world? Sometimes, yes, it does. But that is why we ask these things to begin with. Do not ask a question just to affirm what you think you know. Do not ask a question when what you really want is a compliment. Ask because you want to know more, because you want additional input and because you want to expand on your work. All of that is quite ok, assuming that we react to that quake with grace. It is not always easy. I know this because I have been there, but it is how we grow as artisans.
And yes, sometimes we do not react with grace, but we can learn from that too. The key is to remember that this is not about you as a person. It is not even about the quality of your work. It is also not about the person who took the time to give you critique or engage in discussion with you. Please, please do not turn around and scream about how someone treated you less than kindly when, in fact, they were actually responding to your query.
I would love to see everyone be more willing to have thoughtful, engaging dialog. This is how we all learn and further our knowledge of things from the past.
(Yes, I understand there are people out there that might try to harsh someone on purpose, or people that offer comments that were NOT asked for. This post is NOT about those situations. They happen, everyone on this planet has heard about them at this point. This post is a reminder that it is a two way street and any "someone crushed my dream by looking at me funny" comments will be deleted.)