when dragging and dropping a bookmark from the browser to the sorter or DT icon, DT creates a web archive. Whenever I click on such a web archive, it seems as DT is reloading the original web page.
What would happen if the original web page disappears from the internets?
Would I still have a complete copy (as in archive)? Or am I misunderstanding that concept here?
Yes, you would still have a complete copy of the Web page (except for dynamic graphics, which may be incomplete in the copy).
WebArchive is a proprietary Apple format, so isn’t readable on other platforms. Also, WebArchives have tended to be somewhat flaky, especially older ones, due to bugs in Apple’s WebKit code.
An alternative to WebArchive if you wish to capture a full page is PDF, especially one-page PDF (a Bookmarklet option, and an option in DEVONagent). Such PDFs can be viewed on any computer platform.
I mak most of my own captures as rich text of selected text and images of an article on a Web page.