I prefer to mark scores neatly, making note of specific details or fingerings. What I am not a fan of is the jumbled mess of circles, attempts to circle a given note when the circle surrounds two bars, markings in pen, messy inscriptions, illegible writing, an anything else that marked in an disorderly manner.
One time in university my teacher wanted to indicate some pedaling, and picked up the first writing instrument available - a pen. The pedal marks were as tall as the two staves, and very roughly drawn on top of the staves. I would have gladly rewritten them neatly below the staff, except they were in PEN. From that point on, I always brought a pencil to lesson for my teacher to use.
IMO, inscriptions should be as neat and presentable as the engraved score.