If you add any text besides what you pasted in and than click post/preview does anything show up then?
Yes, I tried that yesterday when I was testing the problem for Duuring. Let's say I also typed up the Summary under the Update, you know "Corsican fighting Austria with Britain, woo scary, Russia doing stuff, It's a European War wooooo". The Summary would show up once I hit Preview and Post, however the Spoiler and everything inside it would simply disappear. And if after posting I quoted the post to see if the BB code was still there, just invisible, the BB code would disappear after posting as well.
I tried it with test posts on the OOC thread and the same problem occurred during my test PM's and even in my PM to Duuring about the issue.
The issue is being resolved by Duuring and the devs, however I just wanted to bring attention to the problem in case any of you all experience it or figure out a way to work around or even fix it.
Major Edit: So I sent BBJ a portion of the update (without detailed information regarding battles/major events of course) upon his request to look into the issue. One of the Battle spoilers in the update that I scrolled up to hide in my screenshots was a naval battle. In the text I sent to BBJ, the battle name and some words were typed. These words were formatted in the usual way I normally type: Font Times New roman, Font size 12, center, etc. He pressed Preview and got the same error that I got. However, upon deleting all of the bb code in the naval battle event spoiler, the message returned to normal and he could preview it no problem. The event obv was just normal standard fse text however it was visible.
We can now reasonably conclude, thanks to BabyJ, that the problem lies somewhere between FSE's BB code and FSE's spoilers. Perhaps some of the BB code bugs out when in spoilers or there is a conflict when BB code is inserted inside a spoiler which is already inside the main spoiler. We still don't know for sure, however it should help in figuring out what exactly the problem is. Thanks to BBJ for figuring out that crucial piece.