Updated the OP, posted v0.3 which brings the wrapper system in line with v7.6.0 changes (note that previous builds should continue to work, they will just have old style elements).
Your server does...
and that sample has nothing in it.
Exactly, it shows that the wrapper works out of the box, without custom coding applied to it; in its purest form you can see that it is working in v7.6.0.
It's probably your bad HTML, you have elements that aren't in quotes, you use the <p> tags like they're <br>'s
Did you come from v7.5.9 or prior? UBB.threads v7.5.9+ are all HTML5 versus xHTML.