This is a pretty sweet hack. One of the hardest problems in categorization is, well, besides appropriate categorizing things (e.g. perhaps I should tag it "Asian" instead of "Chinese", as my notebook will contain a great many variety of cuisines...or "Food", instead of "Chinese"...as my notebook won't contain many food recipes to begin with)...is normalizing those categories...My Pinboard collection is a bit of a mess because some articles I've tagged as "databases" and others just "database"...or worse, "dbs"....but with this hack, you can easily see the number of existing categories and how many pages fit into each category...and since it is a manual process, there's even less chance you'll have a cluttered namespace.
I would add a colour element as well. I've been using coloured pens in business for almost ten years now, and the time saved by having that extra dimension of communication (my Shirlaws team are trained in using the same colour scheme globally) is immense.
Less so for single theme notebooks (like a recipe list) but for journals (use colours for feelings - red = mad, yellow = glad, pink = lovable etc) or business (red = support, blue = cashflow, black = strategy etc) the side-on view would tell you more than just quantity.
If a story has had significant attention in the last year or so, we kill reposts as duplicates. If not, a small number of reposts is ok. Please don't delete and repost the same story, though. Accounts that do that eventually lose submission privileges.
We didn't kill this one, but rather demoted it as a dupe. Killing it would have closed it to additional comments, and we try not to do that when there's an ongoing discussion.
I don't think the hack is the index as much as it is the visual skip-list of sorts, and then being able to jump to the page with the content without having to do a binary search of sorts for the page number you are looking for.
That said, physical journaling is a hard habit to keep :) I feel like I've tried every trick under the sun. Bullet Journal seemed to work for a while, http://www.bulletjournal.com/ [no affiliation], but it's still tough to rigorously keep an index up to date when you just want to jot down something quickly.
I don't see any mention in that entire wiki page of marking the edges of pages vertically for reference when looking at the book from the side. In fact it flat out misses it in the examples, "pointers are typically page numbers, paragraph numbers or section numbers" all of which require you to flip through pages manually instead of just looking at the side and getting a visual.
