Edit: I apologize for the double post - I think I hit a wrong button there - and I can't delete the post .
You can always delete your own post as long as it's the last one in the thread.
As long as there is no other post made, a small "delete" button (in form of a button with a blue 'X' on it) is displayed in the bottom right corner of the post, right next to the "report this post" button (red exclamation mark). Just click on it.
Alternatively, you can hit the "edit" button. Then you get a "delete this post" option in the first line above the edit window.
As said before, both only appear as long as there's no other post made in the thread. So you can always delete the second of the double posts, but not the first.
Take an idea from one person and twist or modify it in a different way as a return suggestion so another person can see a part of it that can apply to the oxp they are working on.