Now that it's just "MongoDB 4.2.6", the title makes me think that this is a release announcement, not an analysis of the software.
The first title (that specifically referenced a finding of the analysis) was best, imo. Mildly opinionated or whatever, but at least it quickly communicated the gist of the post. On the other hand:
"Jepsen: MongoDB 4.2.6" – not super helpful if you're not already familiar with the Jepsen body of work.
"MongoDB 4.2.6" – as stated above, sounds like a release announcement.
If you want a suggestion, maybe something like "Jepsen evaluation of MongoDB 4.2.6"? Not overly specific (/ negative) like the first title, but at least provides some slight amount of context.
@dang