Some people, like me, have only written replies and no root nodes. A reply should always be read in its context hence you likely have to read a whole lot more than just the writeup. Even for root nodes you should read the replies as they might provide enlightening insights on the subject, so I wouldn't say this is a good method to ++ someone. It's a whole lot of work if you just want to ++.
It's a method, but I don't find it very satisfactory.
Update: I'm not sure who you (jeffa) are arguing with in your reply, but I couldn't agree more. I think that in large the same applies to replies to posts too.
See perltoc if you don't know which perldoc to read!