[mattdodge]

This is the shortest one of the solutions so far. Wonder if it's the shortest possible? (Other than empty = empty)

[spacehome]

Yes. It is the unique shortest possible solution if you allow for a repeat at the beginning. OTOH if you disallow starting with a REPEAT, the shortest is length 10.

[daveloyall]

Hm. Well, it was the first quine I arrived at. No special effort was made to make it short.