Not true. There was a study that showed that information density is pretty consistent across all languages, regardless of the average number of phonemes used in that language or the strategies that are employed to encode structural information like syntax. I can only assume you are refering to the density with your statement based on the subject matter in that article as well as the fact that, given enough time and words, any language can represent anything any other language can represent.

I apologise if my terms are not exact, it's been years since I've studied linguistics. In addition, since I'm not going to dig up a reference to that paper, my claim here is just heresay. However the finding lines up with a pretty much all linguistic theory I learned regarding language acquisition and production as well as theory on how language production and cognition are linked so I was confident in the paper's findings even though a lot of the theory went over my head.

How achievable is literacy?

Do you have any evidence of this? I've never heard this claim before.

Vietnamese is one example. Having tones attached to syllables means that words and sentences are shorter. In fact, the grammar is very logical and efficient compared to baroque European ones, especially of the slavic/baltic flavour.

But. The same mechanism in Indo-European languages is used for intonation. we express sarcasm, irony, etc this way be essentially using a single sentence tone.

I have some good Vietnamese friends explaining how hard it is for them to use (and hear) a sentence-wide tone. So, say, some of the fluently speaking Russian Vietnamese always sound like they are sarcastic.

Otoh, I always had problems ordering rice with pork in hanoi...

This does not entail that more can be expressed than other languages. Please see my other reply which goes into (admittedly only slightly) more detail.

Otoh, there should br some connection between grammar complexity and written culture. It is my hypothesis but, say, culture with a rich novel writing tradition leads to a complication of the language grammar. A 3 page long sentence, anyone? One can see how Middle Egyptian literature made the underlying language more complex.

I've sort of thought 60 might be a nice base to work in. Some mathematicians prefer base-12 because it works with a wide number of factors and base-60 is just adding a factor of 5 to base-12. The result would be a base with an even wider variety of factors and, ideally, fewer instances of fractional amounts.

http://www.loglan.org/

Downvotes happen no reason needed.

I bet that could be expressive if not legible.