Maybe it's time for us to consider adopting some guidelines around this issue. We probably all learned pretty much the same "rules" in school about how to cite sources when writing a paper or preparing a speech. Those rules are basically what "fair use" is all about. Internet etiquette is probably much looser but it doesn't have to be.
Here is one very simple suggestion:
When interesting information is discovered on an internet source and you wish to share that info with others, simply provide a link to that source. If someone doesn't want links made to their on-line comments then they shouldn't be posting their info in a public forum.
One obstacle is that a person needs to be a logged-in member on a site like Playmofriends or Klickywelt in order to see photos. In a case like that we can help people figure out how to become members. People can also continue to ask for permission to copy and re-post original photos (just like so many people have already done in the past.)