I think what nirvana is worried about is that this will get simplified to "CouchDB doesn't scale" for developers who don't know all the circumstances. It's the slashdot blurb that landed in the front page of HN, not the sober list post.
It's like saying "$hot-software-de-jour doesn't scale" when the article actually said "we couldn't get it to scale in our server environment - which is a cluster of Arduinos powered by solar cells".
There's nothing wrong with having a workload/architecture/environment that doesn't suit a particular piece of software, and if you do it's right to choose something else that does suit your needs. Saying (or implying) that piece of software is bad because it doesn't suit _your_ strange requirements is about as credible as saying "Photoshop sucks 'cause it can't send email!"