Thin paper is the worst for bullet journaling. It totally ruins the whole creative experience when your work bleeds. Learning to test paper first makes the hobby way more fun.
Ugh, that's the worst. I learned the hard way too. Ruined a whole weekly spread with ghosting. Now I just do a quick scribble test with my heaviest pen in the store. Saves so much headache. Thin paper feels cheap and kills the vibe.