@ashish You're in so much of a rush to reply that you didn't even bother to read my other post below that.
Nice quick edit you made to include my other post in your reply again...
Anyways, reasons are perfectly explained, the community understands it, the moderators understand it and hence the rule is enforced!
A record should be there on this site. There's feedback system which is placed here and when you exchange feedback that feedback is linked to a thread. What's the point of it when that thread is empty?
It is the fault of some members that a free edit option is not provided after some time because they don't want to follow rules. If all community members have to suffer due to it for the safety of them so be it.
Will you take the responsibility of any member's sale thread and buyer's protection if some fraud is done and evidence on threads is removed? No! So manage with whatever we got here, it's basically free so don't complain.