Do or did you ever find it cringy to write on 4channel in your native language ?

nope

Okay if it's with native speakers, rather odd if it's with foreigners who normally don't

Nej då.

Não? Porqué q'eu ia sentir vergonha? Eu adoro a minha língua

Literally no one else here does

nie

It was weird at first, because I hadn't written in German on the web in more than a decade.
/deutsch/ is surprisingly life-like. There are people that actually use that odd terminology IRL. Mostly encounter those people on the train or bus, though. Not at work or on campus.

no, shitposting in finnish is a long-standing tradition on every board

No at all, when speaking with people who understand Ukrainian or telling something about my language. I haven't tried otherwise, 'cuz it does not really make sense

Yes. When I go to /lat/ I feel as if I were on retardland