TL;DR Yes, explanation is always needed. There should be some effort from the user who is writing the answer and should try to produce original content rather than copy pasting from external source. Even if it is from scriptures. Direct quotes from the scripture should be only used as citation and not the only in the answer.
See The copy-paste issue, Hinduism version and How to reference material written by others
This issue had been raised many times by various uses in different communities earlier than this. The conclusion is "Try to explain what you understood and write it in layman terms".
Stack Exchange is a network of Q&A communities about different topics for building libraries of high-quality questions and answers, focused on each community's area of expertise.
The emphasis is on the word expertise. An expert tries to explain a topic with what he had understood in a simpler way along with citations. But a normal person who is a beginner repeats what he learnt. This is where the difference lies. We need to think and write answers like experts rather than a beginner. Providing direct copy paste from an external source is something not "expert" like. Any one can do it if he has some basic knowledge about computers. But we are not a site about computer techniques. We are a site about Hinduism. The quality of the site is enhanced when the topic is well explained. The reader should get an idea on the topic when they read an answer without going to other external source again. That should be our goal.
But the text is explaining everything. Why should I explain again?
This is a common question. When we are pasting some content, that is not yours. Its author is someone else. Pasting them here only duplicates that content here. That adds nothing helpful to the site. If something external is helpful and answering, everyone would need that external source. Why would/should anyone read your answer or find helpful in your answer?
This issue had been addressed by Shog9 while writing a meta post about our site's progress from private beta to Public Beta. In, Private beta extended - please focus on quality he stressed this issue in a separate paragraph
Original content; more than just a Hinduism primer
.And worse yet, an awful lot of them are answered that way: by quoting external sources. A site that just regurgitates things that others have written isn't much good; answers like that just clog up search results without adding anything. It's important to cite your sources, but just as important to demonstrate knowledge of both the question being answered and the topic itself - this is where we can actually make the Internet a better place, demonstrating how to use this knowledge to answer specific questions.
They just give upvotes to the user and helps us to get reputation and privileges but the answers are not much of quality. They neither help site's progress nor the user who reads the answer. I will give an example for better understanding.
Generally, a black cat is considered inauspicious by people. A person got the doubt and asks a question related to it. Now, the main problem starts, there will be answer quoting a huge paragraph from a Purana or a Smriti text about what is considered auspicious and inauspicious. There will be a single line "Because scripture says so" rather than giving explanation on why which is the man question. Users will upvote the answer because it has a quotation directly from scriptures hence there is an effort. But, is it really answering the question and giving the reason? Is there any explanation from the user before quoting or citing (Yes, there is a difference between citing and quoting. We only need citations and not quotes)? The question will be counted an answer, answerer gets reputation and appreciation but the questioner remains with the same confusion he had. The answers should be voted based on how well the answer explains the problem rather than the content from scriptures or sources.
Our former Moderator Mr.Alien predicted that there would be a problem in the long run and it seems to be true. Many users only quote some passages from texts rather than explaining them in their own words. This affects site's quality and progress. Copy paste issue was one of the reasons which prevented the site's progress from private beta to public beta. Our site was in that stage for 2 weeks. Normally, it is only 1 week. We will face the same problem now. This can be a reason why we are still in Public beta stage. If this continues, there will be a large group of users, a handful users with thousands of reputation and many badges after their name but the beta label beside our site's name will also continue even after two more years.
Now the points in the question:
Well, what to say when no effort is noticed in searching the relevant chapter from a valid scripture
I found that by googling "Karna Jarasandh Yudh". The direct chapter was seventh result on the first page. Anyway, as I said earlier in the answer, we should not vote based on finding the chapters. Someone who is very good with searching skills can do that. But the answer should explain what the topic is in layman terms. A person can directly find the chapter through search and find the details from Mahabharata themselves. But they search on the internet in books or watch YouTube videos for discourses etc., . Why? Because the matter will be condensed in an easier form. This is the reason why many great acharyas and philosophers wrote books on scriptures and in an easier matter. Many don't read original scriptures when they are available and look for easy explanations in books or diuscourses. If we are showing them complex translations of the originalsm, we are not helping them.
Due to this reason, I commented on one question instead of answering it as I had nothing to explain or add in the content.
You misunderstood. The question you commented was a resource question. For them, giving the source is enough. We should not comment for them. Add it as an answer. Same for verse identification questions. Giving the source is enough. Explanation is optional. But for story related, philosophy related and other questions, there should be summary of the content in our own words and there should be citations to back up what we say. Some put 100% quote and give a source at the end but that is not a good answer. All the content is by some one else and this user gets the fruits of it by reputation, comments of good answer etc., .
Further I saw few answers, like....
You can ask them to update their answers. Every one are a part of the community. Every one should take equal responsibility of its moderation. If you find something wrong, you can try to correct them. I am sure the other side will also take it positively. You know that the site's policy is. You can show that. One or two users cannot keep track of all the answers posted and comment on them. All should take the responsibility. There is a reason why users are given moderator privileges. So that moderators won't get burden. Don't leave everything on one or two users or moderators. If someone are okay with these type of low quality answers, they should stay silent when the topic of graduation etc., is happening. Users who are asking clarification in comments, asking for sources for the improvement of the answers etc., gain nothing or lose nothing by doing it. They do it for the site's progress. One should join them instead of saying why didn't they do it under one answer. You too have privileges, use them.
Few users say in chat that it's educational site or site not for profit so copy paste is allowed as long as we are providing the source from where we copied
This only applies to Creative Commons license. Some sites follow it and some don't. Hence there can't be a blanket statement.
This can be well addressed on Meta Stackexchange. This is about copyright issue and related to the site's policies. With the implementation of GDPR, many sites are updating their Terms of service and privacy policies. So, we should read their policies very carefully before quoting their content on our site. We all got e-mails from Stack Overflow about update of TOS. Read it. If some external content is reproduced on our site by violating the copyright of the owner, SO may a complaint and there would be problems. Many translations users quote on the site have copyright issues and should not be reproduced. So, we should always give credit to the original translator and author. But some users are copy pasting the summaries of scriptures (let alone original scriptures) too which should be discouraged. We can do it by letting them know about it in the comments and downvoting such type of answers.
By this I don't mean everything should be expert and should be religious way. All types of users are important for a Q&A site. Some questions can be easily answered by a simple google search or finding the chapter or verse. Besides that, we should try to add some explanation to the answer in own words. That is needed from our side because we are a different site. So, our site should have a different content. Read The Inmates are Running the Asylum? . A great pair of Q&A.
Finally, it all rounds up to this: We should be able to explain what we write in our posts and not say "I don't know. It means what it just says. I just wrote what I read or saw. "
If you found out such answers (including mine), let the user know what is wrong in it. Ask them to improve answers. Even moderators are not above the site's policies.