Most of us use the web sites to let our fellow listeners know whats on in real time so we can all enjoy the quality free programming that is on. I don't really expect a qsl for that.
A side benefit of these postings are that the stations can see how they are heard and whether they should continue the broadcast.
Sometimes, people in my general location hear shows better than I do. It's usually explained by a leg of my antenna falling onto the ground. This new antenna is that good! So far. Lets see what winter brings.
I would think that it is useful to the stations that are transmitting to know how well they were heard even if the reception reports are from remote receivers or from their SDR receivers and after the show. I guess to them it's quality control. Some of them really appreciate mp3's of the broadcast so they can tweak things.
As for QSL policies, I would guess each station would have to set their own policy regarding remote receivers, SDR's and lengthy time delays between the date of the broadcast and the date the reception report was sent.
As for logging postings, I think as long as the listeners honestly list what they heard and that they heard it from a remote receiver or an sdr recording on their own SDR, thank the station and send 3 first class stamps to the mail drop they might deserve a QSL card. But again thats up to the stations.
At the end of the day, I'd rather see more postings so more people know that shortwave is still out there.