If I see multiple 'owners' of a page (if I'm looking for a particular page), I usually just assume the latest entry is the most recent known owner. Seeing it show up multiple times can kind of be a testament to how 'popular' it is, despite it being let go of multiple times.
When I have a page where old owners haven't removed the page from their galleries, I just think of it as showing a page's history of ownership. Maybe there is a better way to track this, but it's kind of interesting to see where the pieces change hands and the types of pieces previous collectors have, either to validate your collecting tastes or to get some inspiration from other collections, if you are new and looking to flesh out a theme.
If it's a 'for sale' entry that is not updated, I would just comment "Thanks for the sale, piece came in great shape" or something similar to denote it has been sold without sounding rude, if that is a concern. If it's from a sale previous to yours, commenting from where and when it was sold again to you would seem fine and for someone observing, might actually be useful info.