Perhaps we could have a dropdown box where you could report a player for being extra helpful or otherwise going above and beyond to make your day better. Perhaps someone answered your question politely in tradechat. Or a player asked if you were going for the mining node you were fighting on top of rather than just ninjaing it during your battle. Or maybe someone helped you fight a battle out in the wild that got out of control with adds.
Once someone gathered enough reports of being helpful, what would the rewards be? I would think it would have to be something that doesn't affect gameplay. If it did, guilds may insist on guildies reporting each other has helpful just to skew the system in their favor. Perhaps it would just reward a series of titles. Unfortunately, guilds may still require guildies to report each other in order to get those titles just to collect.