Ultimately, though, there are two reasons it didn’t come back (at least for the time being) :

1) We want to analyze the effects of our current projects (such as Kaplak Stream) on their own first. The Disqus plugin definitely helped the Kaplak Blog reach interested readers. Now we want to see where we stand on our own.

2) Apparently, there’s no easy way to manage several (i.e. a lot!) sites/blogs with one Disqus user account, or accomodate for several owners of a blog or site.

Additionally, it was frustrating to live with someone else’s rigid architecture and wait for the Disqus team to fix things when broken. Now we have our pingbacks back, and can install all the WP plugins we like. Freedom!

You can either add the parameter or just not preview the post while
making drafts.

It gets me a bit uncomfortable, that readers may get incomplete posts or posts subject to later changes (I often write blogposts days, sometimes weeks or months in advance)

Unfortunately, previewing a post in WordPress is the same as viewing a published post. Disqus doesn't discriminate against those types.

In the next version, we will attempt to determine whether the post has a published status and set the parameter automatically.

Daniel also supplied a Javascript parameter by email, which could help avoid this. I still don't understand however, why or how previewed posts in WP could, should or ought to even appear in Kaplak's page on Disqus.