We do have the 'Search for Related Threads' feature whilst making a new topic, so perhaps we could somehow run 'scans' such as this to check all threads on this site for enough words relating to that post. For example:
Some guy posts a thread on 'How to make a Hamachi Server Public' in May.
In early June, another person posts a thread titled 'How to make a private server public with Hamachi'
Someone reading realizes it's a repost and clicks the 'Flag as Re-Post' Button.
The re-post tracker sends out a scan (like searching the site) and searches for related phrases and terms. I know programs like this exist as I go to school and got busted by one.
The tracker detects that the newer post has 70% similarity to the post in May. That post gets 1 strike because more than.. let's say 25% was similar.
Two more people realize and flag it. Post closed.
I have also searched the web for a script like this, but so far I haven't found anything even tweakable to resemble this. I'll keep searching though!
