In the "Family Tree" tree, I just noticed that parents have been added to my paternal line 3rd G-Grandparents. I've been searching for this for decades, and had been fairly confident that this information was lost to history. Yet someone linked parents, and did so without adding a relevant source, as none of the listed sources mentioned anything about the parents. I've written the user, but have not heard back anything.
So a couple related issues -- (1) it would be logical to require adding or linking a source related to vital information like linking to new relatives, so that then anyone can see exactly where that link came from... and with a reminder that whatever source is linked should be directly related to the change being made.
(2) In cases like this, where parents that anyone links is automatically a highly questionable change, it would be great if this could somehow be marked such that when linking parents, they could be forced to see a message. This is where I could explain the parentage difficulties in this case, perhaps explaining that some potential parents have already been disproven, and prompt more productive conversation between researchers. As it is now, one person changes it (without a source), the other person doesn't believe it and changes it back. There's no actual conversation as people don't provide contact information or don't respond.