First, I have no idea how it‘s done online. I simply don’t play.
However, there are issues otb:
How to castle properly? You are not allowed to use both hands.
There are positions where your King doesn’t have to move. What if you touch your King? Actually, there are positions where the King just moves one square. Has he done so the opponent „has the move“ (in principle he could move before the opponent completes castling), according to the rules. How distinguish between K/R move or castling.
One idea: one could change the rule that one always has to start with the „illegal“ part of the castling double-move.
Consistency issues.
First, I have no idea how it‘s done online. I simply don’t play.
However, there are issues otb:
How to castle properly? You are not allowed to use both hands.
There are positions where your King doesn’t have to move. What if you touch your King? Actually, there are positions where the King just moves one square. Has he done so the opponent „has the move“ (in principle he could move before the opponent completes castling), according to the rules. How distinguish between K/R move or castling.
One idea: one could change the rule that one always has to start with the „illegal“ part of the castling double-move.
Consistency issues.

