Hexbear started during the 2020 BLM protests, where cops were using social media and internet presence to track down activists. They are still doing this, but with less vigor than when police stations were burning down.
This included things like using tattoos on naked bodies, etsy store receipts etc.
Just before the r/cth ban, there was also a problem with chasers and leering objectification, and steps were taken to reduce thirst-posting and the like.
These things combined means that people don't post selfies or direct identifying information. People post their pets and artwork, but I know I have to make a decision about where and when I post things to make things non-trivial for cops or random chuds. I feel like a unique pet name, breed, and rough region could be enough to track someone down.
Even so, I think I'm bad at it. I feel like if someone knew me and read everything on hexbear they could ID me pretty easily (and I know multiple people in person on hexbear, but we've never exchanged usernames).
Idk if there are any hard and fast rules beyond the selfies and direct ID though. I should burn this account.
Edit: removed reference to masculinity
For voicing your opinion about activism,
I'd recommend to at least use:
do not post your opinion through your daily account.
Above should cover the needs of most people.
But if you think you're a high profile target,
then following would also be smart:
do not post in similar writing as your main account, e.g. if you usually capitalize each sentence, don't, if you usually use emoji's, don't etc etc.
e.g. no Windows, no Apple, no closed source Android fork, but do use QubesOS, or TailsOS, or GrapheneOS.