I agree, having the title in both languages is probably best workaround for Translation of thread title. (for those interested, there is also related talk about adding synonyms for tags, so discussions used can be found easier by non-English speaking world: Increase the number of tag words allowed - #10 by Matija_Nalis)
But it is definitely welcome to contribute in other languages. I personally use English because I’m more comfortable with that than with automatic translation of Croatian (and I can use the practice), but I’ve seen English-speaking people jumping to Croatian category with posts in Croatian and communicated with them just fine in English / Croatian mix.
As an aside, that however might be more of Chat vs. Forum thing. Firstly, message in chat like Telegram, and message in forum are vastly different in both size and effort to create, as well as in culture behind them (chat is usually considered something temporary which is quickly gone and more informal, and forum is something that stays there forever and will be referenced later).
For example, This one message alone would be at least dozens of messages in telegram. Even in English-only territory, there is much more e.g. daily messages in OsmAnd telegram channel, than daily OsmAnd-tagged messages in this community forum. That is in my opinion normal, and probably for the most part not related to languages.
Now if Chinese community had some other standalone forum (or mailing list) dedicated to OSM, then it would make sense to compare that numbers to community.openstreetmap.org forum - results there would be more language-related I think.
I think having both is best - if you can find three moderators (there really isn’t much of an obligation so it should be possible to find 3 interested persons). Then people who are more shy of western culture can mingle in Chinese subcategory, and those who are more bold can be those who thread both Chinese subcategory as well as elsewhere (currently mostly English-dominated, although many important discussions are happening in German-domainted subcategory too, and others)
There is a saying “Be a change that you want to see in the world”. I would advise that people from wide variety of backgrounds participate in discussions they are interested in - the more they do, the less western-centric those discussion will become.