Remember to set the #language when you're posting in a different language! I'm seeing quite a few people… not doing so, usually in English while claiming to be in some other language. This just isn't right.
Some Fedi clients provide in-line “translate” functions – #glitchsoc's #Mastodon client does, and that's useful; but it's odd seeing that button present for something already actually (in my case) in English, and it's a Bit Less Convenient when it's not (again, in my case) in English but claiming to be as that'll be missing.
Also, it's worth checking when you're replying: the default is taken from what you're responding to.
(Okay, I can usually use my desktop browser's #translation function should I want to, depending on which language it actually is, but I'm not always using that: #Tusky doesn't have any translation function that I've noticed.)