[bskrobisz]

I think these are reasonable. I should highlight, though, that 1, 3 and 4 are true for sign languages as well -- 3 and 4 doubly so (given how large a component individual expressions and gestures play in communication without sound).

[CivBase]

> 1, 3 and 4 are true for sign languages as well

That's true so long as the speaker is the one signing, which is probably true in the context of video calls but probably not in the context of TV.

[SamBam]

I believe 4 is. At least, in the sense that intent, rhythm and emotion can be conveyed by a signing translator better than text can.

[jcrawfordor]

I've specifically heard from a deaf person that they much prefer a sign interpreter over captions because the sign interpreter can convey nuance and mood more reliably than captioning.