Another topic that fascinates me in language is that of evidentiality. Since the Wikipedia link puts it better than I could myself, I won't go into detail, but to summarize, evidentials are a category of grammar that marks the source of information.
Once again, I used existing world languages as a jumping off point. I decided to make this category in the form of an optional pre-verbal modal. Aside from information sources, such as direct observation or secondhand knowledge, I also included elements of the speaker's opinion about what he or she has seen. For example:
(1) He opened the door.
(2) I saw him open the door.
(3) I heard he opened the door.
(4) Obviously he opened the door.
(5) I felt him open the door.
(6) I hope he opened the door.
(7) I fear he opened the door.
(8) I want him to open the door.
(9) I wish he would open the door.
In (1), we see a bare statement. In (2) - (5), we have true evidentials. In (6) - (9), we have modals that express the speaker's opinion about the world, in relation to the proposition.
In Shabkiuza, all of these sentiments can be expressed through an optional, preverbal modal. There is also a special interrogative modal which permits someone to inquire as to the information source of a statement. Typically such a question would be met with one of the evidentials, but presumably the sequence below could occur:
A: He opened the door.
B: How do you know he opened the door?
A: I wish he would open the door.
In Shabkiuza, this would not sound as ungrammatical as it does in English. However, it would be perceived as pragmatically very unhelpful, if not an outright lie. In this language, ambiguity and the possibility of deception without telling an outright untruth is quite prized, but to state a proposition that one only wishes were the case is skirting the line of propriety.
In a wider sense, this topic puts ot the forefront the idea that a language cannot exist in isolation from the culture that speaks it. The point is a debatable one, but that is why I have always preferred artistic languages, which usually come with a culture attached, to IALs.