Security of tokenization of plain text conversations - cryptanalysis
Chinese "looks" encrypted. I believe it to be a marketing gimmick; they want to be able to show "encrypted text" that people will unconsciously associate with notions of unreadability and utter obscurity -- and nothing beats Chinese for that (except in China, of course; if they want to sell their product to China they will have to use Greek or Sumerian scripts).

There are more than 70000 Chinese characters in Unicode, but only 20000 or so in the "first plane" (the code points which fit on 16 bits), which are the most likely to be supported by existing software. This still allows for 14 bits worth of data in each glyph, which is not bad.

As your analysis shows, this appears to be a simple word-based substitution cipher, which will be broken by statistical analysis. People use perhaps 2000 common words, so I suppose that observing a corpus of, say, 30000 tokens ought to be enough to decrypt the whole thing, especially since there is an awful lot of context (on your screenshot we even have the pictures of the individuals involved !). Minoen "Linear B" script was unravelled with less data than that.

No, it is not secure, and hardly "serious".