:(.
There’s a site setting called enable emoji, once that’s disabled they won’t be autoemoji’d. That’s a site-wide setting though, if you’re not an admin you’ll have to live with their decision to autoemoji!
Otherwise you can wrap your emoji in backticks like this: `:)` to get :)
1 „Gefällt mir“
It’s technically possible to spam ZWNJ (it also gets past the minimum length limit) but there doesn’t appear to be an IME that automatically adds the ZWNJ when inserting :( and friends.
Regardless, this is not something that should require an IME-level workaround.