ELU hates discussion because Stack Exchange hates it. This has been the stated case for at least five years, as there was a question in 2011
Why must we "avoid discussions in comments"? and there is current evidence in the moderator messages available.
Stack Exchange sites, of which ELU is one, are Q & A sites. They are not discussion fora. There is a question, and you are welcome to answer. If you agree or disagree with an answer, you can vote on it; you can also provide your own, better, answer. Comments are there for eliciting clarification. Comments are not provided for discussion. Occasionally, a comment might be made pointing out a fundamental flaw in an answer (instead of, or in addition to, a downvote); or adding something worthwhile which doesn't merit an answer of its own. On a question, a comment might be used to provide helpful advice on an off-topic question (so the asker doesn't go away entirely empty-handed), or even to point out a basic error in the premise of the question, or maybe to offer additional corroboration. But comments are not for discussion.
If you want to discuss within the Stack Exchange environment, use Chat. With 20 rep, you can use the main ELU chat room; with 100 rep you can create your own room(s); there are other privileges too. Chat offers one-boxing of posts so it's easy to link discussion to a particular example.
Once the discussion has crystallised into a position, head back to the question and write an answer (or edit the question, depending on what the discussion was based on). Discussing things in comments isn't helpful when what is required on a Q & A site is a succinct question and succinct answers: it shouldn't be necessary to trawl through a discussion to come up with a position.
The system flags excessive comments on a post to draw moderators' attention to something going wrong, and it does that because Stack Exchange is not a discussion forum and comments have a specific purpose. Moderators are expected to do something with the developing situation, and the system offers the opportunity to move comments to a chatroom. Generally, a large number of comments indicates a discussion, so the comments are moved. Sometimes it's not a discussion but rather an argument, in which case different actions may be called for. But long comment chains indicate something is going wrong within the Stack Exchange Q & A model, and they will be dealt with.
As mentioned above, part of the armoury provided to moderators is the moderator message. We have boilerplate templates for a number of reasonably foreseeable situations, and excessive discussion in comments is one of them. You may not have seen it; it looks like this:
We've noticed that you have a pattern of engaging in lengthy discussions in comments, frequently consisting of responses involving multiple, back-to-back posts. Comments are intended as brief messages to provide feedback, add minor information, ask for clarification, or discuss the content of the post. Lengthy clarifications should be edited into the post itself or posted separately as a new question or answer, and extended discussions should be taken to chat. Extensive comment threads tend to be a distraction for other readers. These lengthy discussions are often hard to follow, and can easily hide critical information.
Preferring to argue with other users in comments over revising your questions and answers to address their concerns is a red flag to moderators, indicating you may not fully understand the purpose of Stack Exchange: our goal is to provide readers with expert questions and answers, not host discussion or debate. If you desire conversation, stop into the site's chat room.
The second paragraph there may need tweaking, depending on whether it's sent to the writer of a post or someone who comments on it, but it is a network policy that discussion within comments is discouraged.
Changing a network policy is not actually within the competence of ELU users (including ELU moderators): if you wish to change network policy, you are welcome to ask the question again on MSE, or to provide a dissenting answer to the question linked above — which will also bump that question — for the proposal to be voted on. Make sure you have a fully worked-out proposal and justification before posting.
I would point out now that even if this answer is downvoted to indicate disagreement, policy on this site will not change unless network policy changes (when votes here may be taken into account), simply because it cannot change: the system itself follows the network policy, its processing mandates how discussion is dealt with, and moderators are bound to follow network policy. Meta.StackExchange is the place to initiate changes to network policy.
For discussion, please use Chat: that's what it's provided for.
