Pretty URLs. The POST URL is constructed to have the board id first - and so it's converted to /pub/bugs/?action=... as the intrusion log shows.
What's happening is:
I don't know why Opera's doing that, but that's what's causing this to happen - and note that if Opera behaved as it should, there wouldn't be a problem because the host would be submitted as just the hostname.
We can still fix the URL being generated so that it ends up as wedge.org/do/splittopics but given how Opera is issuing the wrong Host, I'd honestly rather not for the time being until I can find out what the hell Opera (and other browsers, looking at the log) are playing at.