When you are compelled to correct someone on a mod, you have to take into account EVERYONE on the mod. If it is as simple as saying, “Clarify, only Dodge blocks ranged attacks” and moving on, then sure.
However, if you have to bring the entire mod to a halt to clarify something, you may want to consider whether or not it is worth it. If someone calls a Dodge when they should have said Parry, but you would stop the entire mod to inform them: let it slide.
You have to remember that you are playing a game where first and foremost people are trying to have fun. Stopping a mod every couple of minute to clarify rules is not fun. As an NPC, it shouldn’t matter so much to you if someone uses the wrong ability to block what you have, since you are an NPC, and probably a throw-away character.
People are also in a confrontational mood in the middle of a mod. They are often fighting, or at least competing in some way. Trying to correct someone when you are playing their adversary is going to be TOUGH! Granted, everyone knows that it is a game, but they are still in a certain mindset, and it is hard to switch up. If you try and correct them more than once a mod, you run the risk of getting into an argument with them in the middle of a mod, and then you have a shouting match between you and one player, while the rest stand around, embarrassed and bored.
After the mod is over, pull the person aside and clarify the rules with them when tempers aren’t high and action is not flowing. Or you can pull them aside in between action. Say, after you have died, but before you Respawn, pull them aside quietly and let them know about the rules issue. This way, you aren’t in combat, and you aren’t slowing everyone else down.
Mods are no fun if they are stopped constantly. You should attempt to NEVER do something that brings a mod or a scene to a crashing stand-still. If you think you have ability, but aren’t sure, error on the side of the players, and assume that you don’t have it. If a player hits you for a lot of damage, you may as well take it: you are an NPC, you have lots of HP, and players have not a lot of abilities. Let them get the hit in and feel good about it.
A good rule of thumb is to ask yourself is “Will this be fun for the players?” For example:
This guy started a debate about rules in the middle of a mod. I could just let it go and deal later. Do I continuing arguing? Will this be fun for the players?
I forgot some skills I had, can I stop the mod to check my character sheet, will it be fun for the players?
I’ve lost track of my hit points, will dying in a loud way now be fun for the players?
This guy hit me for holy, but I think he meant lightning… Should I correct him? Will the pause be fun for the players?
That last example brings up the second rule to remember: Does this really matter right now?
This guy hit me for holy, but I think he meant lightning… Should I correct him? Does it really matter right now?
I called dodge a second ago, but I meant evade… Dodge is better than evade… I wanted to save it. Do I bring it up? Does this really matter right now?
This guy should be taking double damage from my swings. I think he is unaware of this… Does this really matter right now?
These two questions will help you decide when to correct people and when to just let things slide until you can correct them quietly. Remember: while you may want to correct someone so things are perfectly right, it slows down play for everyone else. Sometimes you have to let little things go, so that everyone can have more fun.