Questions regarding WSC round 13 - Linked

[Richard]

In the Link example, Outside Parity is non-unique.
http://www.sudokuwiki.org/sudoku.htm?bd=...4030046028

Also, could you confirm if all possible circles between two grids are marked? I don't think that has to be the case, but the example has all possible circles marked, so clarification would be nice.

Uniqueness of the example will be fixed in the next version of the IB.

All circles are marked that are necessary to derive a valid solution for the combined grids. It might be possible that on an empty spot a circle can be drawn too.