@oblomov @filobus My guess is that only 0.1% of users would ever use this feature. But the additional UI for it would probably be forced upon everyone.
In many cases I also expect that the manual translation of a non-native speaker is worse than an automatic translation. I see this regularly happen here at work.

@oblomov Honestly, automatic translation has become so good that I doubt it‘s worth adding this complexity to Mastodon/ActivityPub. The UI for making posts already has too many option and buttons and stuff.

Translation can and should be a concern of the client. It works very well elsewhere.