Comment # 1 on bug 1126362 from Wolfgang Bauer

Install the package "webenginepart" and it should work. (you may have to set it
as default in konqueror's settings, it should be preferred if you never changed
that though)

This seems to be a general problem with WebKit, especially as you filed the
very same problem about epiphany in bug#1126249...

IMHO, it's rather a bug in the forum's javascript though that apparently tries
to adapt to the web browser and fails with newer versions it seems (with
QtWebKit4 already too, but there it helped to configure konquerer to identify
itself as Firefox).