Over the years of AL development a few tweaks have been added to everyday speech. Here's a help file about everything to do with the say command.
Alias
The character ' (single quote) is aliased by default for everyone to the say command. So "'hello." is the same as "say hello."
Smiles
A lot of smileys ":)" are handled and can give your speech flavor. Even NPCS can understand them! Saying "I'm going to kill you!" and "I'm going to kill you! ;)" is different. See 'help smiles' for supported smiles. Disclaimer: Many aggressive NPCs will try to kill you even if you don't plan to kill them. A lot of townsfolk don't have a terrific sense of humor too.
Question
If your sentence ends with a question mark '?' the speech is a question.
Exclamation
If your sentence ends with an exclamation mark '!' the speech is an exclamation.
Targets
Start a sentence with someone's name follow by a comma. say to sousily how are you? You ask Sousily "Sousily, how are you?" If someone among you doesn't know each other's names, this form of targeting speech will help them to identify the right person to name.
Continuation
If you end your sentence with a comma ',' and start your next sentence soon after it, your next sentence will be treated as a continuation.