A quick addition I just discovered. I played with creating some simple straight lines by mouse and discovered that only if you rotate the line right after creating it, before changing the color or stroke style or stroke size or anything else, then inkscape actually changes the value of d as you rotate it. This means the program is inconsistent in how it applies rotation, which I think it should not be, so I'm gonna add this as a separate bug if it doesn't already exist.
A quick addition I just discovered. I played with creating some simple straight lines by mouse and discovered that only if you rotate the line right after creating it, before changing the color or stroke style or stroke size or anything else, then inkscape actually changes the value of d as you rotate it. This means the program is inconsistent in how it applies rotation, which I think it should not be, so I'm gonna add this as a separate bug if it doesn't already exist.