To clarify what I meant, I mean that when calling CQ de W___/QRP on the CW QRP calling frequencies one should limit power to 5 watts. Of course it's fine for a higher power station to answer.
When I hear someone calling CQ CQ CQ DE W___/QRP I will generally answer even when he is very weak. When calling CQ and running QRP I get many more calls signing WX7G/QRP then when I sign WX7G.
How about tacking on QRPP when running 1 watt ERP or less, QRP when running 1-5 watts, and LP (low power) when running 5-50 watts? Note that I said ERP rather than transmitter output, since that includes antenna gain, or the lack thereof, if it can be calculated approximately.
A 100 watt rig into an indoor antenna inside a steel-and-concrete building certainly won't generate more than 10 watts ERP or thereabouts to the outside world.