I think you often can't if it's got a reply on it. Your best bet is to edit it. My suggestion is to append a note to it instead of completely removing it or c

I think you often can't if it's got a reply on it. Your best bet is to edit it. My suggestion is to append a note to it instead of completely removing it or changing it, since that alters the record of what really happened, and causes replies to no longer make sense. Adding something like "Edit: Whoops, was just trying to note X, but it didn't come across right." would be sufficient, but it's up to you. To my knowledge, you have until two hours after posting to edit it, so time's running out...