Back in September, eviltrout noted that the branches were split into latest - beta - stable (In increasing order of stability & decreasing frequency of release). There've been a couple discussions around & after that time over on meta.d that basically state that latest has very minimal pre-release testing -- the term they use is "basic smoke testing", which I take to mean "the build didn't break".
Maybe @PJH or @sam can confirm, but I'm 99.99% sure that I've seen referenced at least once since September that WTDWTF is on latest. Not on stable or beta.
ETA: http://what.thedailywtf.com/t/docker-upgrades/1929 - we were on tests-passed (which I believe got renamed to latest) as of July, no notes in the update thread that I could find in a quick skim to suggest it got changed.
The point of my arguing over this point is that, if you want to argue that WTDWTF should be switched to beta or stable branch so that we get more stable forum software, I think that's fair.
If you want to argue that the latest/tests-passed branch should get more pre-release testing before it's put out for public consumption, you have a valid argument but I disagree with your premise, as latest is billed pretty clearly by the Discoteam as an alpha-channel release.
If you want to rag Discourse for having bugs pop into their alpha-quality releases, well, I don't know that anyone here can help you -- the blakeyrant thread is way...