You make a fair point, it is hard to read as a bystander. However I disagree the burden of proof lies with me. I'm not here to convince you of anything, if you want to be sure of something, you must put the effort in like everyone else. Despite that..
Just focusing on storage backends - if you have ever deployed anything that uses BDB (Subversion, Apache, 389, Exim, god knows how many more), one thing you'll become quickly familiar with is it's amazing ability to randomly get into an unusable state, despite an otherwise healthy and unrebooted machine, despite no administrative interference, despite apparently no users or no load at all (e.g. on a Monday morning in a ~10 user office).
My opinions are based on having worked in infrastructure since ~2002, having deployed BDB many times, and having spent many hours trying to figure out how to get an app unbricked without losing its underlying database.
I spent time as an administrator at several companies where Subversion would go down monthly or worse because BDB locking would get messed up like this, and the result is always yet another tarball of the previous database just in case poking it completely corrupts the install. I've had to handle emergency calls because Exim was spewing permanent errors to customers due to a BDB lookup randomly starting to fail.
In other words over the years, like many before me, and for very good reasons, I've come to consider BDB a red flag, and where it goes trouble goes. Put in simpler terms, on a scale of software quality running from 10 ("excellent") to 0 ("crapware"), BDB sits somewhere around -7 ("you had one job"). But don't take my word for it, look at the list of common hazards listed here: https://web.stanford.edu/class/cs276a/projects/docs/berkeley...
Despite that, having deployed OpenLDAP and suffered through its.. suffering.. documentation on several occasions going back ~15 years, including during periods when BDB was the default, post installation I have never once seen OpenLDAP going down. It's very solid software, in spite of prior database engine hindrances.
LMDB is of course no panacea, but having spent years with it as a developer (and maintainer of py-lmdb), I can say categorically that I would not pick BDB over it in any situation, not just due to performance concerns (which are great), but because the design is so damned simple (a single write lock, a single lock file) that I have never once seen it self-corrupt or get wedged in ways that I would have struggled to deal with in my time served an administrator.