Agree with the OP, needs a fix. On NeoGAF this problem doesn't exist, but if there are two threads posted about the same news/topic by different users on the same day the rule is to continue with the thread posted first by timestamp/thread ID # and lock the other, so I generally do the same on this site with double/triple accidental threads by the one user.
Isn't the solution to this issue to prevent new threads posted within a certain time of each other, like 90 seconds or something? (Can't remember if this already exists). Seems the obvious answer, unless the issue is prolonged server responses leading to the duplicate postings.