I understand where you are coming from, but I think that at this point the interpretation of @foo as an idiom for not addressing but merely mentioning a user ha

I understand where you are coming from, but I think that at this point the interpretation of @foo as an idiom for not addressing but merely mentioning a user has permeated most online cultures. Those who really do not know (yet) will quickly understand from context. All in all, I think @foo is less confusing than 'foo, and will spare you questions like in this thread.