Is deleting threads helpful in this forum?

I agree! OP can always edit the question. I would encourage everyone to edit it as the question become clear. Right now, there are many questions that their titles are not-to-the-point and there are serious typos in it.

Many times, I've edit my answer when I read it later and found typos.

There is no edit capability on the comment so far. I would like to have that too.

I think the OP should be able to delete a question when there are no answers (and maybe no comments). Once people have put some effort into answering the question, it should stay. The advantage of deleting unanswered questions is that it might be useful for double posts etc.

There also should be something that makes editing restricted. The OP should not be allowed to delete the text of the question.

Edit: 20-Sept As Walter pointed out, figuring out which questions have no useful answers/comments is difficult. Often a duplicate question will get a quick comment/answer that states it is a duplicate question

I think that when a user requests to delete a question, anyone who has provided an answer or a comment on the question, but not a comment on an answer should be asked for approval.

I am agree with Deniel. Deleting a post should be allowed only for question that is unanswered and not commented.

As author delete the question, it also wash-up the efforts by person who have spent time to find answer of that question.

We need posters to be able to consolidate their duplicate questions down to manageable threads: you cannot rely on the staff and editors to do all that merging on behalf of the posters (for one thing there would be no incentive for the posters not to start new threads, knowing that if they were wrong, someone else will clean up after them.)

If the duplicate threads contain only comments or answers along the lines of "This is a duplicate, please clean up", or even "I already gave you the answer over there", then nothing is lost in deleting the comments and answers.

If the duplicate threads contain real answers or comments of relevance not already expressed, then they need to be merged, which is unfortunately not something that there are tools for even within Mathworks (as far as I can tell.) At least not that preserve ownership and votes and which update "Questions answered" and so on.

If a thread of complete irrelevance to MATLAB is posted, the editors or staff usually find it in due time, but I would not object to someone being able to delete their own completely-irrelevant thread.

If a theory question is posted, then matters get a bit tricky. The question might be expressed as pure theory, or the question might be expressed as how to implement a theory in MATLAB.

The pure theory questions can sometimes be of interest to keep our mental wits sharp even if there is no immediate connection to MATLAB; the poster of such a question does, however, need to understand that obtaining an answer here is sheer good luck and that there are more appropriate resources for (e.g.,) communications theory. Comments about where the poster might have better success are contextually fair and useful comments, but at some point having the posting pruned would be good cleanup. Speaking as an editor, though: I don't like just deleting these and hoping the poster gets the idea essentially, and I don't have time to construct email to them describing why their message was deleted and doing my own research in to where they might better have posted

The questions about implementing a theory in MATLAB: although hypothetically those could be interesting and challenging, it seems to me that the great majority these questions that we attract are from people who really do not know anything about the theory and probably don't really care, but want the MATLAB source code anyhow (e.g., because it would be 95% of the work of their final year project.)

Editing the content of a posting: users need to be able to do this in order to correct typos, fix formatting, add clarifications. And some of that needs to be allowed even after people have answered. None-the-less, if someone asks a homework question and gets a useful contribution, I am not sure that it is fair that they should be able to delete the traces of the discussion afterwards, even if only by editing the content of their question to be "Never-mind; ignore this".

My opinion is that a question can be deleted until it has been answered. Then it can't. Editors, and only editors, should be able to merge questions.

It is infuriating when someone deletes a question with an answer that I've put any significant time or thought into. It's like someone taking your work and flushing it down the toilet, and makes me feel like not contributing any more.

I think we need a "question of shame" where we can answer with names/profile pages of individuals who have deleted questions. Better would be if TMW would just turn off deleting. At this point I would rather have 1000s of duplicate questions, that we can tag as duplicate, then allow people to delete questions along with OUR answers and comments.