He already fully supports modding, considering he did nothing to stop you from making mods.
Unity games by default are subject to reverse engineering, you would think if he didn't want that he would put a system in place like he did for client sided modifications(CheatPunch, EAC, etc).
He allows modding. When I said 'be more supportive of modding', I meant that rather than take a 'do it if you want, but we won't help' stance, he is now taking a 'do it if you want, and we are actually going to help make it easier' stance.
Modding can be done without the developers help, but it's harder if the developer doesn't intentionally build in hooks or at least design the code to be extensible. As good as Minecraft's modding has turned out, it'd have developed faster and allowed for more robust mechanisms earlier if Notch had built in hooks from the get go (and didn't obfuscate the code, but that's another story). Understandably, it's not always a priority.