In addition to that, I gradually switched to their 0.38 pens of different colors. With fountain pen it was more stylish but impractical for multiple semantic(*) colours. With cheap, light, yet nice quality pens of different colours I can not only carry multiple ones, but have the same set at multiple places.
(Dark blue is body text/drawing, light blue is comment/secondary annotation, orange is action/process/message passing, green is data/metadata flow, …)
The coloured trails you can see at more detailed zoom levels, are part of the hiking trail system. The outdoor signage even has a national technical norm [^2] (in Slovak, but has some terminology translated int to English and German).
[1] https://en.mapy.cz/turisticka?x=19.8702765&y=48.7675046&z=14 [2] http://www.jazdecka-turistika.sk/images/stories/dokumenty/KT...
http://www.jazdecka-turistika.sk/images/stories/dokumenty/KT...
EDIT: Typo
Advantages so far: high quality per that works with fountain pen. No fear of ruining whole notebook with an ugly note or a drawing. I can carry only sheets that are relevant to the problem I am solving right now. I can lay out the sheets in front of me to get a bigger picture. I can throw away the bad ones. It is easier to scan (using iPhone scan to PDF function).
https://md.midori-japan.co.jp/en/products/mdpaper-pad/