I'm on board with the idea of reminding people to be considerate to those who are new to the site, but I think there's a piece missing. The new UI element encourages established users to help the new user understand site norms, but I don't see where the system tries to help the new users understand it.
Yes, there's the Help Center, but we already know that way too many users don't read it - and a lot of the information there is not needed before somebody posts a question! I don't need instructions on what to do when somebody answers until after somebody answers. The Help Center simply pushes too much information on the user all at once.
HDE's suggestions for canned comments are great, but several of those could be automatically generated by the system as a new user needs to see them. The system itself needs to encourage established users to provide good feedback to new users, but also needs to encourage the new users to look for, understand, and act on that feedback.
The first time a new user's post is edited, they need to get a notification that says something like:
Another user has edited your post. You can view the edit summary to see what they changed and read the comments on why they did so. You can also add a comment to your post using @[username] to request more information on why they modified your post.
Make the words "edit summary" link directly to the edit history for their post. Fill in the username of the editor so it is easy for them to copy/paste a response if they think something is wrong.
Then give editors a complementary prompt when editing a new user's post:
Dan is a new contributor. Please be sure that your edit summary includes specific feedback on the changes you made so that Dan can understand how to write better posts in the future.
For bonus points, add a couple of checkboxes that the editor can select for common changes (formatted code, changed tags, removal of salutations and "thanks in advance," etc.) and produce canned feedback that expands on those themes. An edit summary that says "remove fluff" gives little feedback to the user, and writing a longer edit summary is a pain for the editor. Make it so that the editor only has to check a box and the new user gets an extra paragraph in the edit summary explaining the "no fluff" policy, with links to the relevant help center page.
The same kind of logic applies to other actions that are typical for new users to experience.
- If they get a down vote, explain to them what that means and link to the help center article on voting. Review the info on how to write a good post.
- As comments start coming in, encourage them to read the comments to see if there is feedback on how they can improve their post.
- Make sure they see a notification about close votes that explains what close votes have been cast and how they should modify their post to alleviate the issues.
- When somebody answers, provide a tip about how to upvote or accept answers, and include guidance on how long to wait before accepting an answer.
- When the user tries to edit their post, explain SE norms like not including "EDIT: " before the new changes, and ensuring that the question doesn't
tl;dr Build the new user experience so that it explains how to use the site instead of relying on users to "be nice" by explaining it to them.
Disclaimer: I haven't done the "new user" experience in a while. Apologies if any of these have already been implemented.