* Paginated content with different filters or sorting? Almost the same content on multiple pages

* Product with a category name in url, or without, or under multiple categories

Both are very useful for humans, but have to be massaged with canonical urls to please Google machines

I'm reasonably sure Google is familiar with pagination and filtering, seeing as that's pretty much the entire thing their own website does.

I don't see how the same product under a variety of URLs, one for each category it's in, is at all useful to me as a human. It actually rather annoys me when the same page has a whole bunch of URLs: I can't tell which is the "real" one, my address bar frecency gets messed up, visited links don't work correctly, etc.

Maybe you run a store where you sell Widget and Deluxe Widget. The only difference is Deluxe Widget has a higher max RPM, but the operating instructions for Widget and Deluxe Widget are identical.

As a consumer, if I came to the website looking for instructions on how to use my [Deluxe] Widget, I would reasonably expect to find the same operating guide on both product pages.

Maybe you should collapse these admittedly identical items into variations of the same product, which will reduce the useless duplicated clutter I'd experience when searching your catalogue.