why not? Obviously, Baidu knows that the copied things are not directly used for commercial purposes (perhaps indirectly), and Baidu knows that it is just a platform for sharing knowledge and answering doubts. This is stipulated in the Copyright Law in China's criminal law. (I'm from Baidu)
There is a provision in the Copyright Law: Item 6 of Paragraph 1 of Article 22 should be the legal provision you want.
Article 22 A work may be used without permission or remuneration from the copyright owner under the following circumstances, but the name of the author and the title of the work shall be indicated, and other rights enjoyed by the copyright owner according to this Law shall not be infringed:
(1) Using a published work of others for personal study, research or appreciation;
(2) appropriately quoting other people's published works in order to introduce and comment on a work or explain a problem;
(3) In order to report current news, it is inevitable to reproduce or quote published works in newspapers, periodicals, radio stations, television stations and other media;
(4) newspapers, periodicals, radio stations, television stations and other media publish or broadcast current articles on political, economic and religious issues that have been published by other newspapers, periodicals, radio stations, television stations and other media, unless the author declares that publication and broadcasting are not allowed;
(5) newspapers, periodicals, radio stations, television stations and other media publish or broadcast speeches delivered at public meetings, unless the author declares that publication and broadcasting are not allowed;
(6) to translate or copy a few published works for classroom teaching or scientific research in schools for the use of teaching or scientific research personnel, but not for publication and distribution;
(7) State organs use published works within a reasonable range for the purpose of performing official duties;
(8) libraries, archives, memorial halls, museums, art galleries, etc. reproduce the works collected by the library for the purpose of displaying or preserving editions;
(9) Performing a published work for free, without charging fees to the public or paying remuneration to the performers;
(1) Copying, painting, photographing and video recording works of art set up or displayed in outdoor public places;
(11) translating the published works written in Chinese by China citizens, legal persons or other organizations into works written in minority languages and publishing them in China;
(12) Change the published works into Braille for publication.
the provisions of the preceding paragraph shall apply to restrictions on the rights of publishers, performers, producers of audio and video recordings, radio stations and television stations.
article 23 when compiling and publishing textbooks for the implementation of the nine-year compulsory education and the national education plan, unless the author declares in advance that the textbooks are not allowed to be used, the published fragments of works, short written works, musical works or single artistic works and photographic works may be compiled in the textbooks without the permission of the copyright owner, but the remuneration shall be paid in accordance with the regulations, and the author's name and work title shall be indicated, and other rights enjoyed by the copyright owner in accordance with this law shall not be infringed.
the provisions of the preceding paragraph shall apply to restrictions on the rights of publishers, performers, producers of audio and video recordings, radio stations and television stations.