I just noticed this question, asked by a new user, which has two downvotes with no comments. I don't think this question is bad—it could use more explanation, and more demonstration of the OP's having put effort into figuring out the answer. But how can the OP know how to improve the question without getting comments?
Is there anything we can do so that we stop discouraging people from asking questions on this site by downvoting them indiscriminately?
There are several reasons to down-vote a post. We have discussed previously (see this and this) that we are not going to require or even demand people to explain their votes. When I see a down-vote that I don't understand I politely comment that I don't understand it, but I think demanding an explanation or stating that there is no reason for the down-vote goes too far. It is not an abuse if people are using their votes in a way different from us.
I have argued a number of times that I am against counter-voting, that is voting to null the effect of another user's vote. Everyone has their own opinion. The total reflects the opinion of the community, it is not the job of any particular user to decide what the total should be. Counter-voting encourages other users to do the same and use their votes to null votes in place of express their opinion about the question. Each vote is a manifestation of some user's opinion and if we respect their opinions then we should respect their votes even when we disagree with them.
I think it is more productive if we comment and explain why we think it is a suitable and interesting question in place of just asking others why they have down-voted the post.
In this particular case, I see several possible reasons for a down-vote.
Formating: It is using an image in place of writing the expression which I think has been one of the reasons people down-vote.
Content: The questions seems to simply ask how to calculate some expression for some particular values. It seems to ask how to apply a method explained in a paper in a particular case in practice. It is too localized and it doesn't seem to be a research-level question in theoretical computer science. It is also unclear what is the trouble the OP is facing in calculating the expression.
If you ask me I think we are being too open right now (I guess it is partly because people get bored that there are not as many questions as they would like) to questions which should not be here and are more suitable for CS.SE. E.g. 1, 2, 3, 4 have been in the closing review queue for sometime but have not been put on-hold. Similarly, it is not clear what this question is asking and should be put on-hold until clarified but it does not have a single close vote. And this is clearly not-research level in my opinion.
I disagree with the premise that every time you downvote, you must always leave a comment. Personally, I used to do that all the time. However, I experienced all sorts of negative reactions: people got upset, they revenge-downvoted my other answers, they flagged my comments as offensive (even when they were neutral and factual). After repeated exposure and getting burnt many times, I've learned my lesson. I know that many others have come to a similar conclusion as well.
While I appreciate others who take the time to comment, and I often do try to comment in a helpful and constructive way, I cannot agree with the suggestion that it is always rude to downvote without commenting. I think the situation is more nuanced, and there are sometimes valid reasons to downvote without commenting. (And don't forget, both upvoting and downvoting are part of the StackExchange model.) While we don't want to discourage all new questions, frankly, I suspect we do want to discourage questions that are off-topic or poorly-explained.
Personally, I think it is the poster's job to understand the culture of the site, read through the help center, read some other questions, and then post a well-posed question that makes it self-evident how the question is on-topic (e.g., in what sense it is a research-level question). While I'm often happy to try to help even new posters who don't do that, I don't agree that it is our moral obligation to do so for every single new poster.
How can the poster know to improve the question? They can read the help center. They can look at other questions that have been posted here. Or, folks (like you) who see something positive in the question can leave a comment suggesting how the question could be improved, or even edit it to improve it.
If you want to help new posters and ensure they aren't discouraged, the best things we can do are:
Leave a comment explaining (constructively and helpfully) explaining the expectations of the site and how the poster can better meet those expectations.
Edit the question to make it a better fit for the site, and to make it clearer why it is a good question that is on-topic.
As a bonus, you might also notice how these are things that you can do, that don't require you to convince anyone else to change their ways. That's a positive thing: that means these are actually implementable. (In contrast, trying to convince everyone to change their ways is not.)
I realize this may be an unpopular message, and I expect to be downvoted (and that's fine). But since you asked, I'm trying to share another perspective.
All I've been able to do is add a comment much like what you did. I completely agree with your sentiment btw.
In the past, we had a meta question about whether we should require downvoters to explain their stance. The concern with mandating this was that people might want to downvote anonymously, which the system allows and which I think is reasonable.
But this shouldn't be abused. In general, I think it's a good idea to wait to downvote when a user clearly needs help reformulating the question, and there are people trying to help.
Maybe this is merely a case of "if you don't have anything good to say, don't say anything"
