I don't think this would be useful
I find it a bit cumbersome that the author is forced to ask a new question for a scenario every time, especially because following questions are often not so hot and risk being closed.
Yes, it is cumbersome to ask a new question for a new scenario. You are supposed to show some work if you ask a question and expect people to spend their time on answering your question. You should put in the effort to make a good question that can be answered in the sites format.
Every different scenario that warrants a different answer than the questions before should be posted n its own so that people may find these different scenarios with the corresponding answers.
The question may not make it to the Hot Network Questions, but your goal should be to get good answers, not make it to some arbitrary hotness list.
Your new scenario will only get closed as a duplicate if it is not different enough from your original question. By making sure to state the differences at the beginning of your question body you can prevent this most of the time.
I have answered one question from Future Historian there and my impression was that the answer was completely drowned out.
You can click on the little arrow on the right side of a chat message to make your post a reply to that one. This makes multiple asynchronous discussions a whole lot easier, especially because the post you replied to is marked and easily visible. By clicking on the portrait of users who are posting a lot at any moment you get the option to click on "Hide Posts" at the end of the upcoming menu to, well, hide their posts. This reduces the noise if there are multiple discussions and you are only interested in one of them. Their profile picture in the upper right hand corner becomes smaller and you can just click on it again and activate "Show Posts" to see them again.
Another thing which wonders me a bit is that there are many people joining the room being completely silent.
I don't see why this is a problem. Waiting to see if there is an interesting discussion or just to get a feeling for what is going on in the room seems pretty normal to me. I don't think we have to press someone into introducing themselves.
superfluous in the main question
Looks like a perfect reason for a relaxed chat discussion.
this information can also be reviewed if someone doubts if the implementation makes sense/is correct (especially hard-science)
You mean like voting an answer up or down and commenting on the specific implementation with comments guided towards clarifying things in the proposed solution, which is often quite long and needs a lot of markdown and MathJax? I don't see why the chat would be a place for this. This is basically why we have answers at all.
I am not alone with this opinion...
Well, you are pretty much alone if that linked question is your reasoning. The question is exactly 2 years old and has +2/-1, so not a lot of sentiment towards one way or the other. But the only answer has +4 and mentions that the chat is the place to discuss and the Main Site is the place for the results of discussions. So quite the opposite of what you seem to propose here. And Aify is using the chat to get feedback, too.
There should be no discussions in comments
If there is something to discuss it should be discussed. That's what comments are for - clarifying problems or misunderstanding that arise because of a post.
If we have three different answers for one question and each has a comment chain, we have three divided chat rooms, tearing apart any cohesion of the question.
Comments are for clarifying the question or answer, depending on where they are positioned. Nothing here gets divided. You are still talking about the implementation of one answer. That's how it should be.
And if we want only discussions in chat rooms, why not open up a specific chat room for exactly this purpose?
If you want you can create a chat room, which is a privilege you earn as early as 100 reputation and post the link under your question or any other question. That would be the perfect place so that everyone sees it and it solves some issues raised by dot_Sp0T in the comments under this Meta discussion like
What if a question doesn't need a chat ever, does it still get one? Are they permanently linked to each other? Who is the room-owner? . I don't think every question needs a chat room. And I don't think every question has multiple chat rooms discussing different answers at the moment. Normally the main chat room is more than enough in my experience if you want to have an open-ended discussion about something.
Sometimes the topic you propose is interesting for the people who are in the chat at the moment, sometimes it's not. Some discussions may be drowned out. Some discussions may go on for days. But this is a problem you will always have with a chat.
Only accepted questions will be discussed.
No. There was a statistic about the acceptance rate before on the SE network, leading to people pestering others about "doing something about your acceptance rate". The thing about accepting an answer is that it is totally, completely, absolutely only up to you to decide whether something was helpful. If you need something different you should ask another question. Or use a bounty for more detailed answers.
As many people here share the idea that an author should wait a certain time until deciding what the best answer is: Only if the author did indeed wait, he/she can use the working room.
I do share this idea, but I have no idea how you want to enforce this. Do you want someone to check everyone coming to the room and throwing them out if they don't meet the requirements? Throwing people out or putting them in the penalty box, the special one that is only for the chat, is only possible by the room owner or a moderator and should only be used for inappropriate behaviour. Not if you have acquired the privilege to use the chat and didn't accept something that was not quite right. This seems to be pretty orthogonal to your basic idea of helping people when they need additional information and want to propose slightly different scenarios. If you can only use the room when you already found your answer, then you already found your answer - right?
Other rooms don't seem to be so popular - there are not enough chatizens
There was a proposal for A chat room for reopening (and closing?) questions that should be used for the usual discussions. VoteOpen was frozen after some time due to inactivity. You have to find enough people to actively do something like your proposal for a longer time period and with a constant influx of new material.
I think the current chat room is enough. If you are bent on having a room for a question and you have at least 100 reputation you can create it for each question where you deem it useful, put a comment with link in the comment section of the question. Maybe we can see this way whether this would be useful or not, which would help in future discussions about this topic. I encourage everyone to give it a try to get empirical evidence supporting either side.