[contrarian1234]

In my (limited) experience private one on one messages are not censored. Or at least this was the case several years back... It's possible things are more strict now.

At least in my tests on Wechat you could discuss tiannanmen square or whatever you want with individuals. Some stickers were censored on Wechat and wouldn't show up. I think images as well may be don't get delivered.

Virtually all censorship and cases of people being arrested are when people talk about these things in large group chats (if a group chat has more than X amount of people it needs to be "registered"). My impression was it's a government fear of things going viral and controlling the public sphere and not about creating a panopticon/state-terrorism

Again.. This might be out of date, but this was at least the case for a long long time.