When replying to a message that had no hard line breaks, the composer inserts them into the quoted parts anyway. This should not be happening (or should be configurable -- whether the user wants the composer to always use hard breaks).
Could you please attach a sample of how the original message looks like and what Trojita outputs?
Created attachment 103459 [details] Message with no hard breaks
Created attachment 103460 [details] Quoted text in composer with hard breaks
Attached before and after screenshots.
Before we go further, could you please clarify what you expect to see and why so? Trojita uses the format=flowed extension which affects the perceived line breaks (and their on-the-wire form, too). If you reply to a flowed text, the composer shows it with apparent line breaks because we have to somehow fit the text into the composer window. The outgoing form is created using flowed formatting once again, and will be re-flowed as needed. Maybe that is confusing for you? In order to reproduce this, please describe a real-world scenario which creates some wrong or misleading result, carefully explain what you expect to get and in what ways the actual result is broken. Then attach raw sample messages including their MIME encoding. You can get these by right-clicking on a message in Trojita and picking "Save Message" or "Save whole message". The resulting .eml files with no additional manipulation or sanitization are important here. Screenshots form both Trojita and maybe another MUA, if relevant, are good to help clarify why the end result is wrong.
(In reply to Jan Kundrát from comment #5) > Before we go further, could you please clarify what you expect to see and > why so? > > Trojita uses the format=flowed extension which affects the perceived line > breaks (and their on-the-wire form, too). If you reply to a flowed text, the > composer shows it with apparent line breaks because we have to somehow fit > the text into the composer window. The outgoing form is created using flowed > formatting once again, and will be re-flowed as needed. Maybe that is > confusing for you? That was indeed confusing to me. I didn't realize the message was then reflowed again. It's fine then. Just to clarify, I was expecting the composer to show the text as on the attached screenshot. It would seem more intuitive to me (I'm used to such behaviour from Kmail).
Created attachment 103463 [details] Composer without breaks