Though I am not a big fan of these, as the src tree would need a massive quantity of these added to make much of a dent at all in documenting what part of what rfc is being implemented, I wont stand in the way of one more near useless comment.
I think the change is useful. The RFC reference could be superseded, but that might also mean the code should be updated as well. It's reasonable to document which version was referenced for the code.
I echo karels' comments that reinstating this provides a reference that one can use for added context, as well as something that acts as a reminder to keep code up-to-date with industry changes. I support re-adding this.