Reply to a post in http://en.wikipedia.beta.wmflabs.org/wiki/Talk:Flow_QA.
Result: form goes away but you don't see your reply.
When you reply again because "What happened to my reply?!?", you see the *earlier* reply, but not the new one
Eric thinks this is a caching bug revealed by Beta labs' slave lag.
This is probably related to Add topic failing on beta labs, which was bug 68531 but has now morphed enough that the original bug summary doesn't apply.