Silent emotes should only be used to express actions that are completely silent. They will only show to people who can see you, so if they are asleep, dying, or otherwise unable to see you, they will not get any indication you did something.
Semote supports a small language which allows you to refer more effectively to other characters. See 'help emoting' for more details on using the language.
You can also use @ to place your short description arbitrarily within the emote.