OK, I see. I can check and uncheck "automatic wrapping" but I'm not sure what exactly it means. The other wrapping options cannot be checked. (Probably they are not checkboxes, they just do something. I'm not sure what they do.) I can reproduce your problem when "automatic wrapping" is checked.

I still think the problem is that logical lines are 72-or-so characters long and displayed on two less-than-72-character-long physical lines.

Suggestion: Try unchecking "automatic wrapping", maybe close and reopen the compose window. If this doesn't helpt: Find out, what "automatic wrapping" and the other options are supposed to do. (Try claws on a desktop computer with different window sizes or RTFM.) Post your findings here or file a bug.

Claws Maemo UI is not intuitive but powerful.