TL;DR: how to address low-quality posts by new-users without being a jerk or otherwise scaring them away?
I'm writing this question after reading this Stack Overflow blog on the need to be more welcoming. This blog focuses primarily on implicit bias (links to accessible BBC article), which I have not perceived as a problem here on ELU (note that I'm not saying it isn't a problem here, I just haven't consciously experienced it as such).
The actual reason I am writing this is not the SO blog, it is because of some run-ins I've had with new users. The problem I experienced is as follows:
I see a new user posting a well-intentioned answer, however, it doesn't meet the standards because it doesn't answer the question or it lacks sources (or both).
In the past I have pointed out my concerns, asking the user to add sources or point out that their answer is interesting but doesn't answer the question. I see how this may come across as somewhat passive-aggressive: in their view they have taken the time to sign-up, write an answer and then I barge in saying I (we, the community) expect them to have higher standards. Obviously I can take a bit more time and sweet talk it a bit, but that doesn't change my message: you (the new user I am addressing) have to put in more effort.
An example of expressing my concerns is the following comment I made:
Please edit your comment in your answer. Also add sources to support your answer if possible. link
The comment is concise, not impolite, but also stone cold, it comes across as ordering the new user around. The new user doesn't feel very welcome and I come across as the bad guy.
Then some other community members add comments, I will cite those as well:
Hi Adam, welcome to the site. It's good that you're enthusiastic (15 posts already!) but I'm afraid they're not being well received as they don't match our site's standards. This site aims for questions to be answered "the way an expert would". This means explaining your answers and justifying them with dictionary definitions and links to them. See e.g. Nigel J's answer for a good example of how to do this.link
Your answers are appearing in the Low Quality review queue and are at risk of being deleted if they're not improved.link
Welcome to EL&U. As AndyT said, there are rules for the site and the whole SE network. You can check these out at the help center or take our tour and visit the English Language & Usage Meta. Thanks! link
Those two users are polite, but I don't think it comes across to the new user as very welcoming. Putting myself in their place I could read into the three comments as follows (in order of the first to the third; playing devil's advocate): 'nice try, but we expect (even) higher standards', 'they are even appearing in the low quality queue now, at risk of deletion', 'here are some links: go educate yourself'.
We could easily vote down, delete or otherwise deter those users, but that's not very welcoming. Furthermore, it counteracts the many calls for attracting more users who are willing to participate.
Defining the problem
Putting it briefly, the problem, I think, is how we (myself included) approach these new users. We (tend to) come across as bossy, ordering them around and saying they aren't doing well enough.
I am not blaming myself or any of the other community members because it really is difficult to say you expect higher standards and not come across as bossy.
Tackling this problem
I am proposing to open a discussion to look into ways of telling new users that their answer doesn't meet community standards without scaring them away.
To do so, I think we need one or two good sentences conveying this and a more extensive explanation in the help centre or on this Meta. Since there are many of these well-intentioned answers we can easily copy these two sentences and a link to the extensive explanation to those new users.
PS: if you think I am reading too much into things and you don't perceive this as a problem then don't hesitate to add a comment (or even an answer if the mods will allow it).
I just found this post on Meta Repository of polite responses. It provides many good template comments, however, I still think it might be a good idea to have some Meta or help centre post to link to (to make sure the new user doesn't feel scolded). There is How do I write a good answer?, but that might need to be extended.