It's pretty clear which posters are new and not familiar with the RD threads. When someone steps over the line, you inform and warn the poster and deal with any further transgressions.
Look, it almost seems as if you want to devise a system which is capable of handling all situations that are thrown at it. Which is impossible. Most of these situations can be easily dealt with using pragmatism.
Are the rules that are in place capable of the goal you've set for the merger and RD threads? Are there not instances where double standards are at work? That's simply what happens when you introduce the human element into the system. And a forum has a particular large human element. So my advise, stop planning, stop trying to envisage the perfect system. We don't have it now, I have been (in my own view of course) shafted by moderation which I deemed unfair a couple of times, and I'm still around because I realise this isn't an exact science. I realise mods have to deal with people who have become quite crafty at being a plonker while staying within the rules.