Well, since I opened this thread and mentioned I wanted to do such a Pull Request, let me respond so some issues raised here. One argument against this - and one that had me going there - was the inconsistency that $0 in messages is part of the same thing as arguments, and that $0 in messages should be the selector. But this has been challenged and shown inconsistent on its own, as then $0 should be the abstraction name, so I'm not convinced.

I actually always thought/perceived $0 as something else, a third usage/case of dollarsigns. I guess many considered so, as many of us were confused as to why not $0 don't work in messages. Hence, I'm actually interested and after a canonical and formal definition of $0, for the sole purpose I don't say stupid things to my students. I checked Pd's tutorial (14.dollarsigns.pd), and it says that the different behaviour in objects and messages "may sound inconsistent, but it's not. Object and message boxes are both actually messages, but in the case of the Object box the message is passed at creation time, and for the Message box, at message time". As I read it, I don't find a conflict or inconsistency if "$0" also gets evaluated and passed at "message time". 

So after all the discussion, I still can't see the issue, as $0 becoming 0 doesn't seem of any use or a good behaviour. But I'm still open to more clarification. Now, a reasoning in favor of adopting this is that Purr Data is using it. Not that I think Pd should really adopt anything that a fork decides to do, on the contrary, but it's hard not to see this does matter, as many users are now comfortable, happy and abusing this feature in Purr Data, and those patches can't run in Pd.

cheers