The existence of {ja’chuq} in the dictionary implies that the direct object is a person. There is no *{jatlhchuq}*.

No, it implies that the object is a person. Klingon has both direct and indirect objects, and sometimes either can be placed in the object position. ja'chuq and yIja''egh imply that the person being told something can be the object, but it doesn't tell you whether that's a direct or indirect object.

A word is not a direct or indirect object by virtue of its position or inflection; it's inflected or positioned according to whether it's a direct or indirect object (and the verbs they're attached to).

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SuStel
http://trimboli.name