How should we respond to questions from unregistered users? Should we treat them differently from questions from registered users?
For example: Should we post comments encouraging users to register? Is it OK to suggest to posters that they might be more likely to get answers if they register, or to judge their question more negatively because they haven't registered yet? Are there any principles we should try to follow?
We should not treat unregistered users any differently.
Stack Exchange does not require registration so we shouldn't infer anything from a user's decision not to register. I suspect that, in this privacy-conscious age, quite a lot of people will be reluctant to register when doing so is optional. Posts should be judged on their own merit, not on whether or not the poster has registered. Even if we feel that unregistered users are more likely to abandon their questions, the question exists for the common good, not just for the user who posted it.
We should also be careful about even encouraging unregistered users to register. As a result of the comment thread that prompted this meta thread, the user whose question was being commented on registered an account. But now they can't edit their own question to improve it...
Whether a user account is unregistered or registered is a technical detail that should not have any influence on how they are treated.
Anyone is free to decline to answer or curate questions from unregistered users, or questions from users whose name starts with A, or questions from users whose avatar includes more green pixels than blue pixels. That's because everyone is a master of their own time and involvement.
On the other hand, to vote differently based on whether a user is registered or not would violate the one rule of voting: vote for the post, not for the user.
If you notice that a user is having trouble because their account is unregistered, then it's ok to guide them towards registration. Don't just say ”you should register your account“. Most users don't even know what that means, and even if they knew, they'd have no reason to do what you say. Any comment that says “you should register” must include two pieces of information: how and why. For the how, link to How do I create an account? from the help center. Note that it doesn't say “register your account”, it says “creating an account”. The terminology around accounts is a bit confusing. For the why, explain how this would solve whatever problem they're having, e.g. that this will allow them to upvote answers (in response to a comment saying ”thanks“).
If a user has lost access to their original account and as a result posts an answer instead of commenting or instead of editing their original question, point them to I accidentally created two accounts; how do I merge them?. Since users aren't notified of comments on a deleted posts except for comments left by a moderator shortly before or after deletion, it's usually up to moderators to leave such a comment, but in case the user does visit the site before the answer is deleted, you can speed things up by leaving a comment in addition to flagging.
A comment like “Here comes another unregistered user (I was planning to write an answer...).” is unhelpful because the target wouldn't even understand what you mean. It's also rude because all the target will see is ”I refuse to help you for some obscure reason, even though I would have helped someone else“. Moderators delete such comments on sight, and repeatedly posting such comments may lead to sanctions.
I have some suggestions:
Judge questions on their merit. Personally, I'd like to judge questions on their merits, rather than by who they are from. I'm not suggesting this as a policy to enforce on others (how could we?), but rather as a goal that I'd like to aspire to. Perhaps you might like to join me in those aspirations?
Be constructive. Let's use comments for material that (a) helps the user improve their post or (b) helps the user. In other words, let's try to make our comments constructive and helpful.
Respect their decision. It's fine to suggest "You might want to consider registering your account; it helps you make sure you don't miss answers", but it is ultimately the poster's decision; let's respect their decision, without giving them a hard time. Let's avoid suggesting "Please register your account; I am less likely to answer if you don't" or anything that could feel like pressuring them to register.
Welcoming in public. We can (privately) use whatever criteria we want when choosing how to vote and whether to answer. However, public comments that are visible to the poster and others are held to a higher standard. I propose we avoid publicly making comments that cast aspersions or negatively judge a post based on whether it is from a registered or unregistered user, or that express frustration with questions from unregistered users, or that imply such questions are somehow less welcome or second-tier, as those could be taken as hostile or unwelcoming.
... as far as content goes. I don't see any reason to moderate or otherwise interact differently.
Of course, it's everybody's prerogative to not answer questions by unregistered users, if they feel they're likely to "waste their time". (I don't hold that opinion, but I've seen it uttered.)
Unregistered users will often run into problem by not being able to edit their posts, sometimes creating strings of posts. They also don't receive notifications for comments or answers. They can't join chat. They can not vote on answers they may receive.
If you perceive any of these (or other) points to become an issue, I think it's fair to tell the user that registering can help. A link to the help article about merging accounts is often helpful as well.
