both down result

[bound for glory]

Both players are knocked down. If either player has the Block skill, they may use it to avoid being knocked down.

Mic drop.

[Fold]

Both players are knocked down. If either player has the Block skill, they may use it to avoid being knocked down.

Mic drop.

Of course it could be yet more concise:
Both players are knocked down. If either player has the Block skill they may use it to avoid this.

Or, you might say that it's obvious that to use the skill he must also have it, and arrive at something like this:
Both players are knocked down. Either player may use the Block skill to avoid this.

Perhaps combining the two sentences works:
Each player is knocked down unless he uses the Block skill.

And perhaps everyone knows that Block is a skill meaning it could shrink to 9 words:
Each player is knocked down unless he uses Block.

Now, while a short rule appeals to me, I don't know at what point the pursuit of a concise rule results in a less clear one

[Steam Ball]

Or, you might say that it's obvious that to use the skill he must also have it, and arrive at something like this:
Both players are knocked down. Either player may use the Block skill to avoid this.

"This"? Both being knocked down?

Perhaps combining the two sentences works:
Each player is knocked down unless he uses the Block skill.

Clearer IMHO and shorter.

[Fold]

Or, you might say that it's obvious that to use the skill he must also have it, and arrive at something like this:
Both players are knocked down. Either player may use the Block skill to avoid this.

"This"? Both being knocked down?

Good catch