I had Corel WordPerfect for Linux.
You could modify the SGML codes to create documents that were compatible with all other versions of WordPerfect and MS Word, but he features that were supported in the document format, but not in the software.
For instance, I could change use more than the 16 colours that the Word for Windows UI allowed you to use, even though the displayed correctly in the WYSIWYG editor and printed correctly.
That was what I was going to say.
That said, if someone detects some sort of data-mining plagiarism bot sucking down everything on an instance, it can be defederated very quickly.