I post in two languages and I'm always concerned if a post from Mastoot will be tagged in the correct one. I'm not sure if Mastoot extracts this from the iOS keyboard language or if it's a trick from Mastodon instance, but I noticed that most of the times my posts are posted in the correct language.

Anyway, it would be nice a visual indicator or, better yet, a language selector in post composer. It gives more confidence having an indicator before posting.