I recently asked a question. I got some valuable comments, but the commenters and I disagreed on a few things. After like 5 comments we reached agreement.
Then @ACuriousMind stepped in and moved almost all comments to the chat. I didn't knew it at the time, but it seems that comments that are moved to the chat get deleted after some time. This makes sense for a chat. But certainly not for comments.
I recently read something new about the topic and thought I could add something to the discussion. However, before that I wanted to reread my question, the answer and the comments. But the now the comments are gone. A valuable piece of the puzzle is now simply missing.
More importantly, the first commenter, whose comment is now upvoted three times and appears undisputed, even agreed that his line of though was wrong - in a comment that is now gone. The content of the discussion has been seriously altered.
What sense does it make to move valuable comments to the chat? I get it, when just two people exchange like 20 four-word sentences. If the conversation is "chat-like" and certainly not valuable in the future, it surely can be moderated. However, when there are long comments that add new perspectives to the question or an answer this is simply ridiculous. Especially, given the fact that the comments that are moved to the chat get deleted after some time. It is not as if these comments would take up space and thus need to get removed.
This type of overeager moderation does not help anybody, except maybe the moderator, who can feel some sense of accomplishment, because he "cleaned something up". It discourages scientific discussions, creates a hostile atmosphere and smells like censorship.