just my .02

When one wants to post to SOPW wouldn't it be possible that when he hits the preview button to start a (super) search on the chosen title of his post and to return the top ten most relevant matches from former posts to SOPW entitled as: "Have you had a look at these previos Questions/ Threads?" on top of the preview page.

But those results shall only be root nodes and not replies as it happens to be when you actually do a search.

In this case one could still hold finishing his post while examining those results and in case cancel his post or proceed if he didn't find an answer.

Have a nice day
All decision is left to your taste