The biggest reason that active players register for TW but don't attack is not because of laziness or selfishness, but because the matchmaking is so bad that there is often absolutely no chance to win. If lack of participation is a problem then isn't it a better idea to address the reasons people aren't participating instead of just identifying the non-participators? I would support the addition of some feature that shows who attacked and who hasn't, but I don't think that it would fix the problem that many guilds have with TW. This change could lead to an increase in attacks due to peer pressure, but from the perspective of a game developer increasing participation by pressuring people to do something they don't want to do is less desirable than the players actually wanting to participate. Without a fix to the matchmaking, such a change would create tension within mid-level guilds between the people who don't want to waste time sending team after team into a meat grinder and the people who demand that you give it your all even in the face of insurmountable odds.
