Min maxers – While I take no issue with people that choose to squeeze every last point to get the best possible dps, I do object to people expecting me to do the same. I play a game to have fun, not to study builds and spreadsheets. I used to play board games and tabletop war games with someone like this and it annoyed the hell out of me while he pored through rule books during his turn to find some obscure rule he could exploit.
Players doing slayer deeds and not acknowledging you – Mob grinding is the same in most MMO’s but in Lotro, unless you get a hit on a creature or are grouped, you won’t get credit for that kill. If I see someone killing multiple mobs in an area, I always offer to group so we are not stealing each other’s kills. It’s a simple courtesy to at least respond. When they don’t, I see red. (Especially when they then make more of an effort to AOE tag every mob before I can get a single hit in.)