surely quotes from his fiction are kosher.

I'm happy to see gems from HPMOR done up in needlepoint and hung on the metaphorical wall of the parlor. But it still smells like trayf! Consider:

Quirrell avoids the ban on quoting himself by attributing the quotation to Eliezer. And he then avoids the ban on quoting Eliezer by pointing out that Eliezer was quoting Quirrell. This is clever and slippery and rabbinical and all that, but it jumps the shark when you realize that Quirrell is not just Eliezer's HPMOR character, he is also probably his LW sock-puppet!