My default place to write something is the Open Thread or a comment on a relevant post. It's only if I realize that an idea needs to be a top-level post (because it's too important and not found elsewhere in a post, or because it's a lengthy development of a key idea) that I make it into one.

As you can see from my two articles, this may be too strict a standard, but I think it's in the right direction relative to the median.