There's slippery, and there's vague. The one that I have not named is certainly being slippery, yet is not at all vague. It is quite clear what he is insinuating, and on close inspection, clear that he is not actually saying it.

However, avoiding qualifiers of uncertainty and not softening one's statements at all exposes oneself to other kinds of dark arts.

Qualifiers of uncertainty should be employed to the degree that one is actually uncertain, and vagueness to the degree that one's ideas are vague. In diplomacy it has been remarked that what looks like a vague statement may be a precise statement of a deliberately vague idea.