Good question. I think that most of the time that's just an indication that the reply would only be of interest to the OP, and not to 'the public'. I've never heard it discussed, but I've thought of it as (more-or-less) a three-tier system:

At least that's how I've thought of it...

In reply to Re: Answering Nodes and Approving them. by pboin
in thread Answering Nodes and Approving them. by ghenry

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