I am likely to write comments in Finnish, English, German, Ukrainian, Russian, Latvian, Estonian, Polish, and Lithuanian.

Most of the comments I write on Piefed are in English because I come from a small country, but I would absolutely prefer them being translated to Finnish instead. Now it apparently works so that I must write comment somewhere in FInnish and delete it so that I will get some French text translated to Finnish instead of English?

And the same, just about a week ago I wrote a comment in Lithuanian. It was just a few words because my Lithuanian has gotten a bit rusty in the 11 years after I quit my university, and my Lithuanian is rusty. Now, if I had wanted a Portuguese text translated after having written that comment, I would have first needed to find some excuse to write a comment in Finnish or at least English or German, because those three are the only three languages in which I can comfortably read a long text.

I would suggest just allowing the user to choose the target language in the settings. Maybe put a tiny arrow next to the globe icon to choose some other language? And then translate by default to the target language that was chosen through that tiny-arrow-menu the previous time?

To underline: You cannot even choose the language a person has used the most, because a lot of people write more posts in English than in their native language. I'm not sure if Finnish is supported as a target language – probably not – but a German person would definitely prefer having German as their target language even if they just took part in a conversation with foreigners. As I am doing right now.

Hm, I'm switching between 4 languages, but OK, at least I really do understand all of them :D