The validator, at least on "advanced validation", should reject placements into an opponent's eye.
In this screenshot, the randombot (white) has submitted a placement at C10, which is illegal as it is surrounded by black stones and thus violates the "no suicide" rule:
Game # 5797941e3a0ac6306cd86c11 (advanced validation is selected for this game)
The validator, at least on "advanced validation", should reject placements into an opponent's eye. In this screenshot, the randombot (white) has submitted a placement at C10, which is illegal as it is surrounded by black stones and thus violates the "no suicide" rule:
Game # 5797941e3a0ac6306cd86c11 (advanced validation is selected for this game)