The intent of Format=Flowed is to allow user agents to generate flowed text which is non-obnoxious
when viewed as pure, raw Text/Plain (without any decoding); use of Quoted-Printable hinders this and may cause Format=Flowed to be rejected by end users.
I disagree with the premise that sending text/plain messages without any (transport) encoding is a worthwhile goal. And so K-9 Mail is always using quoted-printable as transport encoding.
Long lines are preserved and it’s up to the client displaying the message to wrap the text to fit the display width. It seems like a mistake that lists.sr.ht is not doing that.
I haven’t made up my mind yet. It’s certainly not a priority.
Almost all clients will wrap long lines when displaying a message. But not all clients support displaying messages using format=flowed as intended. It feels like the current behavior of K-9 Mail is leading to better results overall.
Not all design decisions are reasonable though. Hard-wrapped text is obnoxious for people who need larger font sizes (for disability reasons) or simply use something that isn’t a VT-100 to read text. The same “issue” exists with Git commit message wrapping and plain text files. It is the time to adopt the responsive mindset in those areas as well.