Blimey. If that isn't Stockholm syndrome, I don't know what is.
Wouldn't surprise me if the Moleskine paper is less than 70 gsm - I've got some notebooks that claim to be 70 gsm, and the paper has a bit more heft to it than the very thin, soft paper in the Moleskines. I do quite like how nice the Moleskine paper is to flick through, but the amount of bleed is a bit much, so while I do buy a Moleskine monthly diary each year - useful layout, cover feels nice, price not ridiculous, the per-month notes pages (that I typically don't use) act as an ink bleed buffer - I'd be a bit less confident that their notebooks would work as well.
For notes, I buy whatever cheap ringbound A4/A5 squared 70+ gsm paper notebooks I can find on Amazon.
There are pens that write well on Moleskine but with good paper you can write with nearly any pen and it won't bleed/feather. Moleskine notebooks look and feel like they are high quality but the paper itself is very poor in quality.
That being said, If the pens one likes to use work well on Moleskine, there's no reason why a person shouldn't use it.
Leuchtterm, Clairefontaine, Rhodia, and Tomoe River are some examples of high quality paper. If you want something that's close but quite a bit cheaper Black and Red has some options that work well even with a flexible fountain pen.
