There are some questions having some links that describe books but that actually direct you to the online-shopping portal.
Is there a reason why we shouldn't remove them? (Assuming that the question is not explicitly "where can I buy XY book?")
Shouldn't we at least know that links where articles are sold are precisely this?
Isn't the name of the title (and author) of the book enough for the interested to look for her/himself?
It seems to be 'allowed', but it is disgustingly commercial: free advertising for one particular distributor. Most often done out of sheer laziness, picking the first link on a goggle search, which is often going to Ummatson or similar.
My suggestion would be to not allow that. We do not need any links to 'buy books'. We might benefit from links that enable readers to find books.
An alternative then would of course be to edit the links to either point to the publisher directly or to a non-commercial institution.
One such would be worldcat.org
Especially older books are often much easier to access via archive.org (compared to Gee-Books).
