So, this is a vast overstatement of the concept. One thread does not an "echo chamber" make. That concept is relevant when considering one's overall exposure to topics, not individual discussions. Folks will still have exposure to differing ideas in the myriad of other threads they have access to on the site.
If folks are trying to actually accomplish or talk about a thing - like, say, trying to build a new subclass for D&D - having the constant static of naysayers trying to tell them they shouldn't do it, or insisting they justify their personal reasons for wanting the thing is generally, and specifically, a bad thing.
But, apparently, you're okay with that bad thing.