There is a difference between squashing together thirty commits of someone working on one concrete thing (I don't need to see all the mistakes and reworks you made, I just want to see the result in a nice, easy to read diff), and thirty commits of someone working on thirty things.
The latter is, of course, wrong as it makes the repo history harder to read, while on the other hand the former improves readability.
It would be nice if in the first case one could annotate those thirty commits in a narrative "here I started another attempt", "this solution could not work for X,Y and Z reasons", "these 8 commits are just typos" maybe with also the ability to only select a subset of a commit.
I've recently added the ability to associate a wiki page in Fossil with an individual check-in or with a branch - as additional documentation about that branch or check-in. This is similar to your concept, if I understand you correct. The Fossil changes have worked well enough so far. But only time will tell if this ends up being a good idea or not, I suppose.
An example is the "About branch begin-concurrent-pnu-wal2" at the top of the page https://www.sqlite.org/src/timeline?r=begin-concurrent-pnu-w... - the page shows all check-ins for the branch, and the Wiki at the top gives a summary of what that branch is about.
Another example is the detailed discussion in the "About" section for check-in https://www.sqlite.org/src/info/718ead555b09892f - important information that records the thinking about this commit but which seems too prolix for a check-in comment.
The latter is, of course, wrong as it makes the repo history harder to read, while on the other hand the former improves readability.