I use pencil on the monthly page of my Bullet Journal. Most of the time when you see Bullet Journal users they only write in pen, either ballpoint, fountain or a drawing pen like the Sakura Micron pens. And yes, I own and use Sakura Micron pens myself depending on what I’m doing.
However, what you can’t do with them is erase them and as a freelancer things move around on me so frequently I cannot write everything in pen because I’d end up crossing stuff out in order to write the appointment in elsewhere and then run out of space, so most of my calendar notes on the monthly page are written in pencil. I almost never write something in pen unless it’s something that can’t be changed such as someone’s birthday.
This is the only place where I use pencil. In the daily record if I discard a task I cross the whole thing out which lets me know later when I see it that I decided to not do it. Erasing it would cause me to possibly forget that I had decided to let a task or project go.
Do you use pencil in your Bullet Journal?