> When we speak, we frequently start a sentence not knowing how it's going to end.
> We pause and insert filler words to give us time to form our thoughts.
> We use ambiguity because sometimes we just don't know precisely what we're trying to say
> (Lojban has, if I recall correctly from Okrent's book, over 30 ways to say 'and').
> Forcing people to have a complete understanding of what they want to say before saying it
If you are undetermined, you use the undetermined option, the vague one. You don't really make a decision for that.
Planning is not required for adding parenthetical information. You use it on the spot where you happen to want it.
If you don't recognize that you want to erase a mistake, you just don't use the erasers.
I'm not a native English speaker. When I started learning and speaking in English, I would think to myself, "Ok, the word "which", when used after a slight pause, which corresponds to the comma in writing, it means a non-restrictive relative pronoun, which is what I want now, so I'm going to use it that way". As I kept practicing the language, I internalized the rule, becoming less and less actively conscious of it. Lojban is no exception. I have already internalized some parts of the grammar to which I used to pay much attention in my earlier period of learning.
Also important to note is that, what English expresses with non-verbal properties such as intonation, Lojban can do verbally. When you orally say something in English which you would put in a parenthesis in writing, your speech act are still subject to some phonetic principles such as inserting a pause, changing the rhythm, lowering the pitch, using less breath, and so on. You consciously or unconsciously have to be in command of these properties if you are to successfully deliver your utterance. A particular combination of these non-verbal phonetic properties is what Lojban expresses with to ... toi, the parenthetical markers. Whether or not you are actively conscious of them is a matter of internalization. Just like an experienced English speaker not always actively thinks about each noun's grammatical number in their utterance but still manages to add the plural marker "s" where appropriate, an experienced Lojban speaker would be able to correctly start a parenthetical note with "to" but without always actively checking whether or not that's what they really want to say.
> I realize at this point, I'm getting beyond my own knowledge of Lojban, but I just want to make the general point that being able to be ambiguous does not automatically afford the advantages of the natural ambiguity in "natlangs."
Could you give me an English example with such advantages?