I agree with Pilot6. While reviewing, and also while noticing deleted posts on questions I browse outside of review, I see numerous "me too" posts where someone is really trying to add new information about their related problem. These users should post questions instead, and we should encourage them to do so when we can.
Although terdon is correct that "me too" additions are not valuable, often people who have the same problem as described in an existing question (or believe their problem is the same) want to post so they can add information about the problem as it affects them, and provide details about their situation that they think may be relevant to the problem. What that means is that:
- Their situation is actually different, or
- they think their situation may be different, or
- they can provide information about their situation that goes beyond what has been provided in the existing question.
That means they really have a new question. It's a related question -- except when people are totally mistaken about the similarity to an existing question, which is also something that happens, and then it's not even related -- but it is a new question. It might one day be closed as a duplicate of someone else's question once that question has an answer, or the earlier question might end up getting closed as a duplicate of theirs, but when someone has information about their own problem that isn't captured by an existing question, they have a new question.
When a new question links to an old question, they appear on each other's lists of linked questions.
By the way, those of us who do have enough rep to post comments should post our new questions as questions, too.
The other dimension of this, though, is why do people think they need to post comments to get help? Part of it is that people are accustomed to using forums, which encourage them to post on existing threads. The Stack Exchange system is non-intuitive to many people. Even highly experienced users who have been involved since the earliest days of the Stack Exchange network have occasionally come back after a period of inactivity and posted non-answer answers.
So that's why we have the review queues. When things that aren't attempts to answer a question get posted as answers, we tell people what to do instead and delete those posts.
And I think this offers some insight into why so many newcomers to our community feel powerless that they cannot yet post comments. It's because reviewers keep wrongly telling them that what they really want to do is post a comment.
We have official guidance about what comments are for, but reviewers keep advising people that their posts should be comments in situations where those rules explicitly state it is wrong to do so. The biggest irony is that the wrong advice is often given in the form of an incorrectly chosen canned review comment that itself links to that page.
It is sometimes correct to advise someone that what they've posted as an answer is the sort of thing that ought to be posted as a comment. However, comments are not a catch-all for content that is posted in the wrong place, needs improvement, or need not exist at all. Before telling someone that what they have written as an answer should be a comment instead, I recommend:
- Checking that it is at least not wrong to post it as a comment.
- Considering if the author should instead post a question, even if they would need to provide more information or a better explanation for their question to be answerable.
- Considering if the author should have posted an answer, just not the one they did post. (And when what someone has posted is an answer, just not a very good one, please remember that answers that are wrong, partial, or low in quality do not make appropriate comments.)
- Considering if the author should instead have submitted an edit to an existing post. This is perhaps the least common situation. When someone is posts a "me too" answer, even with potentially useful information, that should still virtually never be an edit. But there are other situations where someone's post is really an attempt to improve another post (usually an answer) without changing its meaning, and an edit would be appropriate.
- Considering if this is a post would not be useful on our site in any form. "Me too" non-answers that provide no additional information shouldn't just be reposted as questions, but they shouldn't be comments, either. (On the other hand, it may be reasonable to encourage someone to post a question with full details of their problem.)
- Considering whether or not the advice is useful to them or likely to result in them using the site better (or otherwise lead to a better outcome for anyone). This may sometimes be hard to know, but in some cases it clarifies some of the other considerations. For example, if I encounter a post while reviewing and I think to myself, "This looks like a comment... but this person is really trying to get help with their problem, and if they post a comment it won't help them or anyone else," then I've figured something out about would and wouldn't help that person.
Occasionally I have heard people express the concern that if we tell people to post questions, we'll have more bad questions on the site. The thing is:
We can tell people what they need to do to ask a good question. We can even show them the official advice.
Questions can be voted on, edited any number of times by their authors and others, commented on specifically, reviewed, closed (if appropriate), and reopened (if appropriate). Totally useless questions can be deleted and useful questions that turn out to be off-topic for our site can be migrated. Negatively scored questions are shown far less often on the front page, so they rarely prevent other good, answerable questions from getting answers.
Speaking of deletion, and the concern about littering the site with bad questions: The system automatically deletes many such closed questions, and question deletion is more transparent and more readily reversed when mistakes are made than comment deletion. I'm not saying we shouldn't delete worthless comments--of course we should. I'm saying that that if we are going to have low-quality content on the site, it should be in the form of posts, which can be both improved and curated in ways comments cannot.
I cannot think of any way to clean up comments anywhere nearly as effectively as the system makes easy for posts. (I suppose this could be achieved by mass-flagging based on SEDE queries, but that's controversial, an outright no-no at least on Stack Overflow, and if done enough to make a big difference would be a massive drain on the time and energy of both flaggers and moderators.)
Suppose a new, 1-rep user needs help with a problem, posts a non-answer, and it is deleted. But before it is deleted, they get a comment telling them they really should post a comment, and can do so once they earn more rep. And imagine that's what they do -- they think, "Well that's weird, I thought this was 'Linux for human beings,' but whatever -- if this is what I need to do to get help, so be it." So they put some time into the site, get their 50 rep, and post a comment. But since Ask Ubuntu is a question-answer site but not a forum, this doesn't get them any help with their problem.
That's a bad outcome -- for that user, for our site, and for the Ubuntu community.
If someone came along and proclaimed, "Ask Ubuntu is a great place for low-quality content that will help no one ever, so long as it's posted in thousands of comments strewn all across the site!" we would know they were mistaken, and suspect they were trolling. So let's stop nudging the whole community in that direction.