[robotresearcher]

Wikipedia says:

"the stronger player will typically play with the white stones and players often agree on a simple 0.5 point komi to break a tie ("jigo") in favor of white."

Which suggests ties can occur in practice with human players, but are then broken wrt an external parameter.

In terms of optimality, is it known in Go whether an optimal player can force a win against (i) all suboptimal players; and (ii) another optimal player, based on whether they play first or second?

I realize we don't know the optimal policy but sometimes we can decide (non)-existence anyway. Anyone happen to know for Go?

[kotach]

The questions you pose require solving the game, at least (ii).

https://en.wikipedia.org/wiki/Solved_game