I absolutely cannot stand medium nibs, it's horrible for smaller or narrow handwritings. Also, with a decent quality paper F nibs are just as comfortable to write with.
Try a Kaweco or Lamy medium nib with a Kaweco or Lamy blue ink. It doesn't write bold. Same can be said with Lamy nib + Lamy black ink.
Medium can mean a lot of things. My Parker Vector's medium nib with Parker's own ink is equal to broad on many other manufacturers. Kaweco's medium is almost equal to Lamy's fine.
All nibs become quite comfortable after they are shaped by your hand and writing :)
I have used Lamy M nibs for several years during school and they're too broad for my taste. Now, after several years of trying pencils I'm using a Faber-Castell studio with an f nib and it's very smooth, even with standard pelikan ink.
Medium can mean a lot of things. My Parker Vector's medium nib with Parker's own ink is equal to broad on many other manufacturers. Kaweco's medium is almost equal to Lamy's fine.
All nibs become quite comfortable after they are shaped by your hand and writing :)