I wrote:
For any starting position (after removal of strings of stones that do not reach empty), a stone is unconditionally alive with suicide allowed if, and only if, it is unconditionally alive with suicide prohibited in the position derived by removing all opponent stones. The proof is easy, using that - if suicide is allowed, the opponent can change the starting position to the derived position; - even with suicide prohibited, the opponent can change the derived position to the starting position.
This "proof" is wrong, as it could be impossible to perform suicide and change the starting position to the derived position: .O.OXX OOOOX. XXXOXX XXXX.O The first argument should be changed to - if suicide is allowed, the opponent can change the starting position to the derived position, or to a position with less stones (thus less unconditionaly alive stones); François Grieu