In my opinion the one rule that is the most annoying personally is the rule that P+K vs N+K or P+K vs B+K is a loss if the side with a pawn times out (unless the pawn is an a or h pawn), for two reasons:
1. If the pawn is neither an a or h pawn, the king cannot be mated unless the pawn underpromotes, which in this endgame is incredibly stupid unless there is some situation I am not aware of that leads to stalemate if the pawn promotes to a queen.
2. In lichess, most players either have auto-promote to queen turned on or promote to queen if premoved turned on. Most cases where this rule applies is in time scrambles during bullet, in which case the player with the pawn will likely premove the promotion.
I understand the rule that by FIDE rules P+K vs B+K and P+K vs N+K flags are losses because it is possible to lose as the side with the pawn, but unlike OTB chess matches which normally have increment lichess games often don't, so this rule applies much more often on lichess than OTB.
1. If the pawn is neither an a or h pawn, the king cannot be mated unless the pawn underpromotes, which in this endgame is incredibly stupid unless there is some situation I am not aware of that leads to stalemate if the pawn promotes to a queen.
2. In lichess, most players either have auto-promote to queen turned on or promote to queen if premoved turned on. Most cases where this rule applies is in time scrambles during bullet, in which case the player with the pawn will likely premove the promotion.
I understand the rule that by FIDE rules P+K vs B+K and P+K vs N+K flags are losses because it is possible to lose as the side with the pawn, but unlike OTB chess matches which normally have increment lichess games often don't, so this rule applies much more often on lichess than OTB.