There are some SEO reasons for mirroring the "Title for search engines" field. This mirroring can be easily disabled. There are two ID fields in the advanced settings in Administration that you can change in order to do this and in the attached pictures you can find the path to them. In "Mirrored control id" you can change "PagesNameFieldControl" with "codeBehindTypeElement" or "SeoTitleFieldControl" for example. After saving these changes "Title for search engines" field can be edited separately from the "Name" field.
have you changed the values for "Mirrored control id" in both FrontendPagesEdit and FrontendPagesCreate? Editing and creating a page are two separate processes and you have to change two separate options to disable the auto fill. I have tried to disable it on my test project and everything works as expected for creating and editing a page.Regards,