I thought the parent comment was referring to real offline journals made of treeware.

Exactly. It's not that I don't see value in online alternatives, but in this case, if the main point is to access it offline, I don't see how different it is from a physical journal.

Why use digital formats offline:

  - editing and reordering text
  - attachments
  - aesthetics
  - accessibility 
  - hassle/weight optimisation

Aesthetics includes theming, and also not everyone has good handwriting.

Accessibility, because not everyone is able to hand-write in the first place.

Weight optimisation, because if a laptop is non-negotiable, going digital means one less thing to remember about and carry with you.

I have multiple physical notebooks/calendars and a digital commonplace book, they all have their place.

For slow writers but quick typists, an app is always going to win out over a physical journal. Also interested in an event call export + parse.