User blog comment:Supahbadmarine/Official Canon Policy/@comment-3258762-20130219102314/@comment-3258762-20130220140922

5: If it is well-made, certainly, it could give some fun, fanmade insight into the Dark Age, but if it is badly written then no. Being that good fanfiction that has no major backstory to be based around is rare, I believe it speaks for its own case.

6: No. We've had this talk several times before. Marines turn to chaos, yes, but Chaos is a pantheon of gods that can manipulate anything. The Tau have no way of manipulating Space Marines like that.