Since this keeps happening to me and I usually know how to use a computer, I'm just going to report it as a bug.
On Google Chrome, v31.0.1650.63 m, using Windows 8.1 64-bit, using the "Post" button will sometimes post the same comment or even thread twice in a row.
Steps to Reproduce the Bug/Issue:
- type a reply into the reply box, click "Post" once.
Sometimes, the post will appear twice.
The post appears only once.
This probably has something to do with the current (=slow) web server.
- more on this you can read in this thread: http://divegame.net/node/7042
That was also a bug I reported :)