Claims about the relative simplicity or complexity of different languages are rarely grounded in actual linguistic evidence. Languages comprise so many parts that it's not even clear what the basis of comparison could be: is English, a language with highly restricted word order but without grammatical case marked on most nouns, more complex than Russian, a language with comparatively free word order but a highly arti…
I don't quite understand your comment in relation with the article. The main subject isn't the complexity or simplicity of the language but rather that it's not effectively used by the population at large which makes it a relatively inefficient tool for communication. He mentions that the language "has fewer words than most languages" but that's not his main point. This text is also clearly not meant as a treatise of…
Emphasis mine.
I don't mean to say that some languages aren't more difficult for speakers of a particular language to learn--no doubt French is easier for English speakers to learn than Chinese. A speaker of a different language that is also tonal would likely find Chinese easier to learn, though. What you're really measuring is not complexity but similarity.
You have a good point that some languages may have more difficult writing systems than others. Linguists traditionally don't consider orthography to be part of a language proper, as a language can have multiple writing systems (like Serbo-Croatian) or none at all, but you're right that most people don't make that fine a distinction between language and writing system.
I didn't mean to be overly critical of the article, which I mostly enjoyed, but saying that a language is "simple" or "rigid" carries a lot of cultural and political baggage--think about how Europeans of the colonial period denigrated African languages, or how in the United States, Australia and Canada indigenous children were punished for using their own language.